Patches Revised For AMD Zen Based Hygon Dhyana Server CPUs
Written by Michael Larabel in Hardware on 11 August 2018 at 04:46 PM EDT. 4 Comments
Patches have been revised for the Linux kernel to support the initial Hygon Dhyana server CPUs that are the licensed AMD Family 17h "Zen" technology, basically the EPYC server CPUs for the Chinese market.

Back in June the initial Hygon Dhyana Linux patches were posted and today they were revised for the third time. V3 of the Hygon Dhyana patches are re-based against the latest Linux 4.18 development code and rework some of the vendor checking codes for improved consistency.

These first Hygon Dhyana CPUs are basically re-branded AMD EPYC CPUs, but there are various identifiers that need to be updated for the family series, PCI Express device vendor ID, and CPU vendor ID.
The first generation Hygon's processor(Dhyana) originates from AMD technology and shares most of the architecture with AMD's family 17h, but with different CPU Vendor ID("HygonGenuine")/PCIE Device Vendor ID (0x1D94)/Family series number (Family 18h).

With these kernel patches, the Hygon CPU support is in place for KVM, Xen, ACPI, CPUFreq, Spectre V2 mitigation, and other bits in common with x86 AMD EPYC CPUs but requiring these new IDs.

The patches for now can be found on the kernel mailing list while they might be merged to mainline in a few short days for the Linux 4.19 kernel cycle.
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