Ubuntu
intel-microcode package

intel-microcode update disables AVX-512 on Alder Lake

Bug #1979123 reported by Lastique
6
This bug affects 1 person
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intel-microcode (Ubuntu)
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Bug Description

Updating intel-microcode to 3.20220510.0ubuntu0.22.04.1 results in AVX-512 inaccessible on Alder Lake CPU, even if the BIOS supports it and it is enabled in the BIOS. The problematic firmware is /lib/firmware/intel-ucode/06-97-02.

Last known working version of intel-microcode is 3.20210608.2ubuntu1. That package version does not contain the microcode (presumably, the version loaded by the BIOS is used).

Please, provide a way to disable this microcode update or blacklist its loading on boot.

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: intel-microcode 3.20220510.0ubuntu0.22.04.1
ProcVersionSignature: Ubuntu 5.15.0-39.42-lowlatency 5.15.35
Uname: Linux 5.15.0-39-lowlatency x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu82.1
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Sun Jun 19 02:24:19 2022
InstallationDate: Installed on 2015-05-01 (2605 days ago)
InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
SourcePackage: intel-microcode
UpgradeStatus: Upgraded to jammy on 2022-05-14 (35 days ago)

Revision history for this message
Lastique (andysem) wrote :
Revision history for this message
Alex Murray (alexmurray) wrote :

You can disable microcode loading by adding the kernel boot option dis_ucode_ldr in your grub configuration.

Revision history for this message
Alex Murray (alexmurray) wrote :

Also can you please report this issue upstream to Intel as well so they are aware of it? https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/

Revision history for this message
Lastique (andysem) wrote :

Reported upstream: https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/61

Revision history for this message
Alex Murray (alexmurray) wrote :

Thanks - FYI - this change appears to have been intentional from Intel - https://www.tomshardware.com/news/intel-nukes-alder-lake-avx-512-now-fuses-it-off-in-silicon - although it is not mentioned anywhere in the release notes for the 20220510 aka IPU 2022.1 microcode update - https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00601.html or https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/releases/tag/microcode-20220510

Revision history for this message
Lastique (andysem) wrote :

I know they are disabling AVX-512 in Alder Lake but for those lucky that have chips with it enabled I think there must be a way to keep it enabled.

Revision history for this message
Alex Murray (alexmurray) wrote :

As I said above, you can disable loading of microcode in Ubuntu via the dis_ucode_ldr kernel command-line parameter by adding this to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and then running update-grub - but then you won't get the other benefits of the updated microcode (vulnerability fixes etc).

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