nvidia-peermem "Invalid argument" on Ubuntu — Fix GPUDirect RDMA with DMA-BUF


TL;DR: If modprobe nvidia-peermem fails with Invalid argument (-EINVAL) on a system using the inbox Ubuntu InfiniBand stack (rdma-core), the module is not broken and you do not need it. nvidia-peermem requires an API that only exists in MLNX_OFED. On Hopper/Blackwell...