Updated AMD Zen 1 Through Zen 3 CPU Microcode Published

Written by Michael Larabel in AMD on 10 April 2022 at 05:45 AM EDT. 24 Comments
On Friday AMD published new CPU microcode files for both Family 17h and Family 19h for Zen 1/2/3 processors. At the moment there isn't any public insight into the changes with this updated microcode but it may be significant.

AMD on Friday published new CPU microcode files for both Family 17h (Zen / Zen+ / Zen 2) and Family 19h (Zen 3). Sadly as is normal, the microcode binary update comes without any public change-log.

But it does seem a bit different this time around with Family 17h being included too... We see Family 19h CPU microcode updates every few months but it's been a while since the last Family 17h update. The AMD Family 17h CPU microcode included in linux-firmware.git was last updated in December 2019. Not only has it been a long time since the last in-tree update, but this new microcode is much larger. The Family 17h microcode goes from 6476 to 9700 bytes in size.

The Family 19h microcode meanwhile is the same size as its prior update from back in February.

Raising my curiosity/concerns about this AMD microcode update is that it's the first Zen/Zen2 CPU microcode update for linux-firmware.git since the end of 2019 and this update is much larger than prior versions of the microcode. The Zen 3 microcode is updated too but that has been happening every few months for the current-gen hardware.

With no official announcement yet on the new CPU microcode we are left to only speculate what may be changed in this version... But given the Family 17h conditions it's likely one of two: just a lot of routine fixes/updates included over the past 2+ years and only now deciding to bundle it up into a new version or the new CPU microcodes are being published now with some security mitigation(s). It very well could be the latter, but we'll see soon if that's the case.

For now the new AMD Zen CPU microcode is on the mailing list but should soon make it into linux-firmware.git and in turn pulled by the various Linux distributions for packaging up nicely for end-users.
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