From my experience, accessing system RAM from the GPU is so slow, it might as well count as "does not work". It's orders of magnitudes faster to memcpy large swaths of memory that you are going to use to the GPU, rather than accessing system mem from a kernel which then takes ages to wait for that small block/page of memory, then waits again for the next small page/block of memory, etc. Latency hiding doesnt work anymore if the latency is that large.

But then you can use CPU/RAM offload, which already allows you to offload without a kernel module.