I could not make Xen work on 4.14.98 but I have it running on 5.4.70 and the USB mouse and keyboard are working properly, even when plugged at runtime. I have used default Xen configuration for Linux DomU /etc/xen/domu-imx8qm-mek.cfg. So migrating to 5.4.70 should fix the issue.
Android and Linux is booting ok in the virtualization? The usage of external mouse trough USB should be in kernel configuration, or check if the mouse is present in /dev/usbX.
I could not make Xen work on 4.14.98 but I have it running on 5.4.70 and the USB mouse and keyboard are working properly, even when plugged at runtime. I have used default Xen configuration for Linux DomU /etc/xen/domu-imx8qm-mek.cfg. So migrating to 5.4.70 should fix the issue.
"Android and Linux is booting ok in the virtualization? The usage of external mouse trough USB should be in kernel configuration, or check if the mouse is present in /dev/usbX."
In response, I checked that there is no device in /dev like /dev/usbX..
The "i.MX Virtualization User's Guide" seems to be a quite old document, please check instead "Chapter 12 Virtualization" in i.MX_Linux_Users_Guide. For Xen hypervisor there is an example of DomU configuration that contains USB configs.