New Linux Patch Officially Confirms AMD Family 26 As Being Zen 5 CPUs
Going back to last July there were Linux kernel patches referencing new Family 26 (Family "1Ah") processors that we assumed at the time were for Zen 5 given how AMD typically handles their family/model IDs. Since then they've continued enabling more Linux device driver support for Family 1Ah.
With a new patch sent out on the Linux kernel mailing list, they are formally making the connection that Family 1Ah (26) is in fact for Zen 5. The new patch today is adding an X86_FEATURE_ZEN5 feature flag, similar to the prior generation Zen feature flags to make it easier for handling different erratum and processor bugs. With this patch, X86_FEATURE_ZEN5 is being set for Family 0x1a for 0x00 through 0x0f (15) models.
With not reserving all Family 26 models for Zen 5, it's possible any future Zen 5+ or Zen 6 processors may be added to AMD Family 26 too, just as Family 25 spanned Zen 3 through Zen 4 and Family 23 was Zen 1 through Zen 2.
In any event the new patch just adds the X86_FEATURE_ZEN5 feature flag and connects it to Family 26 models 0 to 15 but doesn't make any other changes or add any new functionality. As there's been various other Family 26 enablement happening already within the kernel, by the time the next-generation AMD Ryzen and EPYC processors ship the open-source Linux support will hopefully be all aligned nicely... The one area we haven't seen any Zen 5 (znver5) activity yet is on the open-source compiler support with GCC and LLVM/Clang.
While on the topic of AMD Family 26 / Zen 5, the previously-reported AMD PMC driver support for this new generation will land for Linux 6.8. Those AMD PMC driver patches were queued this week into platform-drivers-x86.git's for-next branch ahead of the Linux 6.8 merge window opening next week. With this Zen 5 feature flag patch being quite trivial, it too will likely end up as Linux 6.8 material.
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