Comment 4 for bug 1987567

testing on jammy:

Launch/Setup:
---

$ multipass launch -c 2 -d 8g -m 2g -n xj jammy
$ multipass shell xj

$ sudo apt update && sudo apt install -y xen-system-amd64

$ sudo vim /etc/default/grub.d/50-cloudimg-settings.cfg
# ... GRUB_TERMINAL=serial, GRUB_TIMEOUT=5, GRUB_TIMEOUT_STYLE=''
$ sudo update-grub && sudo reboot

$ virsh console xj

Before:
---

$ dpkg -s grub-common | grep Version:
Version: 2.06-2ubuntu7

$ sudo apt install -y microcode-initrd

$ grep module2 /boot/grub/grub.cfg | grep -v vmlinuz
 module2 --nounzip /boot/microcode.cpio /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio /boot/initrd.img-5.15.0-56-generic

$ du -k /boot/initrd.img-* /boot/microcode.cpio
36092 /boot/initrd.img-5.15.0-56-generic
4936 /boot/microcode.cpio

$ sudo reboot # fails
...
[ 2.100482] Freeing initrd memory: 4936K
...
[ 2.799346] VFS: Cannot open root device "UUID=..." or unknown-block(0,0): error -6
...

After:
---

$ sudo add-apt-repository -y ppa:mfo/build-proposed
$ sudo apt install -y grub-common

$ dpkg -s grub-common | grep Version:
Version: 2.06-2ubuntu7.2

$ grep module2 /boot/grub/grub.cfg | grep -v vmlinuz
 module2 --nounzip /boot/initrd.img-5.15.0-56-generic
 module2 --nounzip /boot/microcode.cpio
   module2 --nounzip /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio
   module2 --nounzip /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio
   module2 --nounzip /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio
   module2 --nounzip /boot/initrd.img-5.15.0-56-generic
   module2 --nounzip /boot/microcode.cpio

$ sudo reboot # works
...
[ 2.675755] Freeing initrd memory: 36092K
...