The "Chinese EPYC" Hygon Dhyana CPU Support Still Getting Squared Away For Linux
Written by Michael Larabel in AMD on 23 September 2018 at 08:23 AM EDT. 3 Comments
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Back in June is when the Linux kernel patches appeared for the Hygon Dhyana, the new x86 processors based on AMD Zen/EPYC technology licensed by Chengdu Haiguang IC Design Co for use in Chinese data-centers. While the patches have been out for months, they haven't reached the mainline kernel quite yet but that might change next cycle.

The Hygon Dyhana Linux kernel patches have gone through several revisions and the code is mostly adapting existing AMD Linux kernel code paths for Zen/EPYC to do the same on these new processors. While these initial Hygon CPUs appear to basically be re-branded EPYC CPUs, the identifiers are different as rather than AMD Family 17h, it's now Family 18h and the CPU Vendor ID is "HygonGenuine" and carries a new PCI Express device vendor ID, etc. So the different areas of the kernel from CPUFreq to KVM/Xen virtualization to Spectre V2 mitigations had to be updated for the correct behavior.

The AMD EPYC Linux support itself has been in great shape since these competitive server CPUs began shipping last year, as covered in many benchmarks on several different EPYC SKUs since that point.

Published on Sunday is now the v8 patches for this CPU support. These patches have been tested on "HygonDhyana SoC silicon" and doesn't affect the kernel support for existing AMD Linux customers. The new patch revision fixes a boot issue while v7 came out recently too with various other fixes and is re-based against the latest Linux 4.19 state.

The Hygon Dyhana Linux kernel support appears to be mostly settling down, so it wouldn't be surprising if this gets queued soon for merging into the Linux 4.20~5.0 kernel.
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