Comment 13 for bug 1732028

It does not consume "a lot" of CPU but lets try still to slow it down into the error.
$ sudo apt install cgroup-tools
$ sudo cgcreate -g cpu:/cpulimited
# you might want to ensure that cpu.cfs_period_us: 100000
# e.g. Set 10% as hard limit
$ echo 10000 | sudo tee /sys/fs/cgroup/cpu,cpuacct/cpulimited/cpu.cfs_quota_us
# This was done on the Host, all tests run in the qemu guest (as on LP), move qemu in those cgroups
$ for task in $(ls -1 /proc/$(pidof qemu-system-x86_64)/task/); do echo $task | sudo tee -a /sys/fs/cgroup/cpu,cpuacct/cpulimited/tasks; done;

I tested different shares using TCG in the guest.
50% seemed to be a tradeoff that isn't too slow to totally fail or having you wait too much.
It gets slower, TCG&Emulation blocked at 50%, vcpus at ~12%

With that I was able to hit this locally:
[ 432.218071] systemd[1]: Timed out waiting for device dev-disk-by\x2dlabel-UEFI.device.
[ TIME ] Timed out waiting for device dev-disk-by\x2dlabel-UEFI.device.
[DEPEND] Dependency failed for /boot/efi.
[DEPEND] Dependency failed for Local File Systems.
[...]
You are in emergency mode. After logging in, type "journalctl -xb" to view
system logs, "systemctl reboot" to reboot, "systemctl default" or "exit"
to boot into default mode.
Press Enter for maintenance
(or press Control-D to continue):

From here going step by step down to the smallest test (this was full autopkgtest).
And there we can again start trying tweaks as in comment #5 and comment #6 but hopefully iterate faster on them.