I've added a 32GB RAM card to my PL and it is working properly, and the addresses are valid and accessible (tested with Xilinx test, and using devmem on PetaLinux).
The problem is that it is not visible as a memory device under /proc/iomem, or using the "free" command.
I have added it to my system-user.dtsi file, and it appears in the pl.dtsi file as well. My base memory is 2GB on the PS side, and it shows up. The DDR4 base address is 0x0048 0000 0000.
How can I make the memory region visible to the kernel?