Arch Linux

Hello everyone, I encountered a problem while trying to shut down my laptop (on top of which runs Arch Linux with the current latest version of systemd (245.6-8)). I also installed and configured plymouth from the AUR. In the last couple of days I set up KVM on Arch Linux (host) and I installed many other programs, therefore I can't say for sure that this is a KVM-related issue. I guess it has to do with my Arch Linux configuration.

What is the problem:
At shutdown some error messages are displayed (if I press ESC immediately after the plymouth logo shows).
If the hook "shutdown" is present, the picture of the logs is the one where ioctl cannot be removed.
If I remove the hook "shutdown" from my mkinitcpio.conf (and I issue "sudo mkinitcpio -p linux"), the message looks slightly different (other picture)

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My systemd-boot configuration file looks like this:

title Arch Linux Kernel
linux /vmlinuz-linux
initrd /intel-ucode.img
initrd initramfs-linux.img

options cryptdevice=UUID=[my UUID number]:ArchPad root=/dev/mapper/ArchPad-root quite splash rw loglevel=3 rd.udev.log_priority=3 rd.systemd.show_status=false systemd.show_status=false vt.global_cursor_default=0 net.ipv4.tcp_ecn=0 intel_iommu=on plymouth.enable=1

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If I set intel_iommu=on (like above), the errors present in the files will be displayed. What is weird is that the laptop for some reason will hang with the monitor still powered on (therefore I could take my time to take the pictures).
Else, if intel_iommu is set to off, the laptop will shut down immediately, without needing to force the shutdown by pressing and holding the power button. The logs will still be there though.

I would like to enable Iommu, but more importantly I would like to understand why those errors appear, and how to fix them.

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Output of 'sudo dmsetup ls':
ArchPad-root (254:1)
ArchPad (254:0)

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Output of 'sudo dmsetup table':
ArchPad-root: 0 948822016 linear 254:0 16779264
ArchPad-root: 948822016 16777216 linear 254:0 2048
ArchPad: 0 965606031 crypt aes-xts-plain64 0000000000000000000000000000000000000000000000000000000000000000 0 8:2 4096

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Output of 'dmsetup info /dev/mapper/ArchPad'
Name: ArchPad
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 254, 0
Number of targets: 1
UUID: CRYPT-LUKS1-[some_ID_removed_by_me]-ArchPad

Output of 'dmsetup info /dev/mapper/ArchPad-root':
Name: ArchPad-root
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 254, 1
Number of targets: 2
UUID: LVM-[some_other_longer_ID_removed_by_me]

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Additional info:
I use zram, setted up following these instructions https://wiki.archlinux.org/index.php/Improving_performance#Swap_on_zRAM_using_a_udev_rule

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/etc/fstab output:

/dev/mapper/ArchPad-root / ext4 rw,relatime 0 1

# UUID=[some_ID]
/dev/sda1 /boot vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 2

# forget about swap ... I now use zram
# UUID=[some_UUID]
# /dev/mapper/ArchPad-swap none swap defaults,pri=-2 0 0

# zram
/dev/zram0 none swap defaults 0 0
/dev/zram1 none swap defaults 0 0

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I tried multiple solutions from different forums, but none worked.