Add "dis_ucode_ldr" to linux boot options for Recovery Mode

Bug #1831789 reported by Jeroen Bobbeldijk on 2019-06-05
18
This bug affects 3 people
Affects Status Importance Assigned to Milestone
grub2 (Ubuntu)
High
Tyler Hicks

Bug Description

Due to some recent problems with a microcode update which broke booting of some laptops I suggest adding "dis_ucode_ldr" to recovery mode boot options to allow booting after a bad microcode update.

See the following topics that describe the problems:
 - https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1829620
 - https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/1

When such problems occur it's very hard to see that the microcode loading is the issue, the booting just hangs at the purple screen, even removing "quiet splash" or using the recovery option will not show the error.

We'll need to double check that dis_ucode_ldr works as expected across all architectures.
According to the kernel docs (Documentation/admin-guide/kernel-parameters.txt), dis_ucode_ldr is x86 only, so my guess is that it will be ignored for other architectures. According to the kernel code (arch/x86/kernel/cpu/microcode/core.c), dis_ucode_ldr works for both AMD and Intel.
I have some time tomorrow on test this on a ARM device.

This was also discussed Ubuntu Developer mailing list where it was suggested to post this here, see: https://lists.ubuntu.com/archives/ubuntu-devel/2019-June/040725.html

Jeroen Bobbeldijk (jerbob92) wrote :

Related to #1829620

description: updated
description: updated
description: updated
description: updated
description: updated
Tyler Hicks (tyhicks) on 2019-06-05
Changed in grub2 (Ubuntu):
status: New → Triaged
importance: Undecided → High
Tyler Hicks (tyhicks) on 2019-06-07
Changed in grub2 (Ubuntu):
assignee: nobody → Tyler Hicks (tyhicks)
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