xpmem_make returns -1, MMIO read fault?

[devreal]

I am unable to use xpmem on my local laptop (Linux Mint 20.2 Uma). I built xpmem, signed the kernel module, loaded it and when I run xpmem_make it returns -1. The last two messages below seem to be appended to dmesg every time I call xpmem_make:

[ 2450.718135] XPMEM kernel module v2.6.5 loaded
[ 3165.159169] nouveau 0000:02:00.0: Enabling HDA controller
[ 3165.262314] nouveau 0000:02:00.0: bus: MMIO read of 00000000 FAULT at 6013d4 [ PRIVRING ]

Linux kernel version:

$ uname -r
5.13.0-27-generic

Has anyone seen this? Any idea what is going wrong here?