As a workaround, add the kernel parameter iommu=soft to use a software replacement for the IOMMU hardware. (See this documentation for details.) This may cause a slight processing overhead.
Open a terminal window and chroot into the local installation
sudo manjaro-chroot -a
If it is btrfs, you need to mount it beforehand, since it cannot be detected automatically.
Open the GRUB configuration file for editing. You can do this by running the following command with administrative privileges:
sudo nano /etc/default/grub
This will open the GRUB configuration file in the nano text editor.
In the GRUB configuration file, locate the line that starts with GRUB_CMDLINE_LINUX_DEFAULT. This line contains the default kernel parameters used by GRUB. It may look something like this:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
Append iommu=soft to the list of kernel parameters within the double quotes. Make sure to separate it from other parameters with a space. For example, the updated line should look like this:
Save the changes and exit the text editor (in nano, you can do this by pressing Ctrl+O, followed by Enter to save, and Ctrl+X to exit).
Update GRUB with the new configuration by running the following command:
sudo update-grub
Reboot your system for the changes to take effect:
sudo reboot
After rebooting, the iommu=soft kernel parameter should be added and active during the boot process. You can verify this by checking the kernel parameters using the cat command, like this:
cat /proc/cmdline
You should see iommu=soft listed among the kernel parameters.