[Bug 1831789] Re: Add "dis_ucode_ldr" to linux boot options for Recovery Mode

[Julian Andres Klode]

** Description changed:

- 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.
+ [Impact]
+ 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
+ 
+ [Test case]
+ Check that dis_ucode_ldr is present on Linux entries
+ 
+ [Regression potential]
+ If you actually require microcode updates to get into userspace, your recovery option won't work anymore. Does this happen? Seems unlikely.

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https://bugs.launchpad.net/bugs/1831789

Title:
  Add "dis_ucode_ldr" to linux boot options for Recovery Mode

Status in grub2 package in Ubuntu:
  Fix Released
Status in grub2 source package in Xenial:
  New
Status in grub2 source package in Bionic:
  New
Status in grub2 source package in Focal:
  In Progress
Status in grub2 source package in Groovy:
  Fix Released

Bug description:
  [Impact]
  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

  [Test case]
  Check that dis_ucode_ldr is present on Linux entries

  [Regression potential]
  If you actually require microcode updates to get into userspace, your recovery option won't work anymore. Does this happen? Seems unlikely.

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