[Bug 1779092] Re: [regression] cyclic reboot caused by the amd microcode updater

[Tyler Hicks]

I wanted to shed some more light on this issue and our decision making
after hearing of at least one person that saw this update and thought
that this was a regression in the microcode provided by AMD. While we
don't yet know the actual cause of this issue, a regression introduced
in the microcode itself is not at the top of our list of suspicions. We
haven't heard of any similar reports in Ubuntu 16.04 LTS, Ubuntu 17.10,
or Ubuntu 18.04 LTS which all received the same microcode updates.

We suspect that it has something to do with the combination of 3.13
kernel's support for early microcode loading, the packaging for the
amd64-microcode package, and/or the initramfs generation when injecting
new AMD microcode. We're still investigating the cause and will release
additional updates when we've tracked down the solution.

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https://bugs.launchpad.net/bugs/1779092

Title:
  [regression] cyclic reboot caused by the amd microcode updater

Status in amd64-microcode package in Ubuntu:
  Fix Released

Bug description:
  It happened like this:

  using kernel 3.13.0-144 (14.04) - ok
  jun 9: installed kernel 3.13.0-149 and rebooted - ok
  jun 21: installed some updates including update to the cpu microcode which was set up to execute at the next boot
  jun 28: rebooted to the same kernel 149 and the system went into cyclic reboot: shows grub screen, when the default kernel is selected reboots immediately with no messages and without creating any logs, nothing in /var/log with appropriate times
  booted to 144 - no issues
  tried upgrading to a new kernel (151) - same cyclic reboot
  booted back to 144

  I am not telling the microcode update is the culprit, but it is mighty
  suspicious. It cannot be uninstalled using standard tools without
  uninstalling the kernels packages (linux-generic, linux-image-generic,
  linux-generic-pae, linux-image-generic-pae). I have both intel-
  microcode and amd64-microcode installed (CPU is AMD phenom X4 975).

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: xorg 1:7.7+1ubuntu8.1
  ProcVersionSignature: Ubuntu 3.13.0-144.193-generic 3.13.11-ckt39
  Uname: Linux 3.13.0-144-generic i686
  NonfreeKernelModules: nvidia
  ApportVersion: 2.14.1-0ubuntu3.29
  Architecture: i386
  Date: Thu Jun 28 13:04:38 2018
  InstallationDate: Installed on 2011-08-18 (2505 days ago)
  InstallationMedia: Kubuntu 11.04 "Natty Narwhal" - Release i386 (20110427)
  SourcePackage: xorg
  Symptom: display
  UpgradeStatus: Upgraded to trusty on 2014-10-18 (1349 days ago)

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