I enabled the CMA (CONFIG_CMA=y) for an x86 machine on Linux kernel v5.10. When I boot the system the CMA reserved memory, but when the graphic card driver i915 or hda_intel is loaded the system crashed. I see the same error with Linux kernel v5.15.
I see that ioremap on RAM at 0x0000000000000000 - 0x00000000d0000000 get fail. When I blacklist the i915 and hda_intel module the system boots fine with cma memory reserved.