[Bug 1918265] Re: Random boot failure with Ubuntu 20.04 / grub 2.04 and Hyper-V 2012r2

[Chad Mikuta]

Hello,
We are experiencing the same issue running 20.04.2 with the exception of the crashing. We have fully updated 2012R2 hosts and when we use VLANs 20 or 40, there's a good chance the VM will get stuck in kind of boot loop when we try to restart it. This doesn't happen all the time either which is odd. When we use VLANs 21,22,41 or 42 for example, the VM seems to boot fine every time. I have tried this on different hosts with different hardware as well with no change in behavior. We've also noticed this same behavior in CentOS 8.

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Title:
  Random boot failure with Ubuntu 20.04 / grub 2.04 and Hyper-V 2012r2

Status in grub2 package in Ubuntu:
  New

Bug description:
  Hi,

  We are experiencing some weird boot issues with Ubuntu 20.04 and
  Hyper-V 2012r2.

  In two cases the installation started successfully, as did the VM
  initial boot and then issues started to arise, where the boot process
  started to fail.

  grub start, the menu pop-up and then just after loading kernel and
  initrd (tried to put some echo(es) in the config the VM somehow reset
  and the menu pop-up back again.

  After a few of thoses either the VM shut-down or the boot is
  successfull, It seems completly random..

  Here it is captured on video:
    https://www.youtube.com/watch?v=5Bk3S-YGDZk

  If i setup a direct EFI-STUB boot of the kernel+initrd the boot
  process works every times.

  I suspected the "save_env/load_env" for a while but a stripped down
  grub.cfg give the same result..

  > insmod gzio
  > insmod part_gpt
  > insmod ext2
  > set root='hd0,gpt2'
  > if [ x$feature_platform_search_hint = xy ]; then
  >  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  94ebc17e-6aca-4e42-b489-b3eaa8a32d90
  > else
  >  search --no-floppy --fs-uuid --set=root 94ebc17e-6aca-4e42-b489-b3eaa8a32d90
  > fi
  > linux	/vmlinuz-5.8.0-44-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro nosplash elevator=noop 
  > initrd	/initrd.img-5.8.0-44-generic
  > boot

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