[Bug 1911959] [NEW] Fresh Ubuntu 20.04 won't boot after intel-microcode update on ThinkPad T460s

[Markus Konrad]

Public bug reported:

Installed Ubuntu 20.04 from USB disk using the first Ubuntu 20.04
installation image released end of April. The system installs and boots
fine. Then, I run a system update via `apt update && apt upgrade` with
updates to Ubuntu 20.04.1. intel-microcode is updated on this occasion
to version 3.20201110.0ubuntu0.20.04.2. Update installation succeeds but
subsequent reboots most of the time fail. I can access GRUB but a normal
boot of any of the installed kernels results in either a black screen or
a screen with a cursor blinking ad infinitum. Booting in recovery mode
via GRUB and then "resume" works, but external display is not detected
in this case. Sometimes however (maybe 1/5 of the time), making a reboot
from this state works.

When I uninstall intel-microcode via `apt purge intel-microcode` the
problems disappear. I can boot the system without any problem.

I had occasional boot problems already since several months, but they
could be resolved by just rebooting (pressing the power key for a long
time). After the latest update, this wouldn't work anymore, so in the
end I tried out re-installing Ubuntu which resulted in the problems
described above.

I'm using a Lenovo ThinkPad T460s with system firmware version N1CET37W
(1.05) which is quite old.

** Affects: intel-microcode (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1911959

Title:
  Fresh Ubuntu 20.04 won't boot after intel-microcode update on ThinkPad
  T460s

Status in intel-microcode package in Ubuntu:
  New

Bug description:
  Installed Ubuntu 20.04 from USB disk using the first Ubuntu 20.04
  installation image released end of April. The system installs and
  boots fine. Then, I run a system update via `apt update && apt
  upgrade` with updates to Ubuntu 20.04.1. intel-microcode is updated on
  this occasion to version 3.20201110.0ubuntu0.20.04.2. Update
  installation succeeds but subsequent reboots most of the time fail. I
  can access GRUB but a normal boot of any of the installed kernels
  results in either a black screen or a screen with a cursor blinking ad
  infinitum. Booting in recovery mode via GRUB and then "resume" works,
  but external display is not detected in this case. Sometimes however
  (maybe 1/5 of the time), making a reboot from this state works.

  When I uninstall intel-microcode via `apt purge intel-microcode` the
  problems disappear. I can boot the system without any problem.

  I had occasional boot problems already since several months, but they
  could be resolved by just rebooting (pressing the power key for a long
  time). After the latest update, this wouldn't work anymore, so in the
  end I tried out re-installing Ubuntu which resulted in the problems
  described above.

  I'm using a Lenovo ThinkPad T460s with system firmware version
  N1CET37W (1.05) which is quite old.

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