Follow-up: Trying to make NVIDIA GPUs plug-and-play on Macs. Found hidden RDMA symbols Apple doesn't want you to see — zero-copy GPU memory sharing might already work.

TL;DR: My last post about testing TinyGPU attracted some interest. This is the follow-up. The Blackwell card is detected and the driver loads, but NVIDIA's GSP firmware fails to boot through TB5 (known issue, I'm working with tinygrad on it). While debugging that, I went down a rabbit hole and discovered that Apple's RDMA subsystem accepts Metal GPU buffers for zero-copy network transfers - something nobody has documented. I also found hidden ibv_reg_dmabuf_mr symbols in Apple's libibverbs that suggest GPUDirect RDMA might be possible on macOS without any kernel modification.