NVIDIA's Graphics Driver Will Run Into Problems With Linux 5.3 On IBM POWER

For those using the NVIDIA proprietary graphics driver on an IBM POWER system, it could be a while before seeing Linux 5.3+ kernel support. Upstream has removed code depended upon by the NVIDIA binary driver for supporting the POWER architecture and as is the case they don't care that it will break NVIDIA driver support since it's binary/out-of-tree.

The POWER changes for Linux 5.3 remove NPU DMA code. In the pull request they do acknowledge this DMA code is "used by the out-of-tree Nvidia driver, as well as some other functions only used by drivers that haven't (yet?) made it upstream."

The patch removing the NPU DMA code by Linux kernel veteran Christoph Hellwig does acknowledge this basically reverts the POWER support for NVIDIA NVLink GPUs. The code is being dropped since it's no longer being used by the in-tree kernel code and thus a burden when it comes to maintaining the upstream DMA code.

IBM developer Alexey Kardashevskiy did warn that this particular code is "heavily" used by NVIDIA's graphics driver. Hellwig responded though that "Not by the [driver / code] that actually exists in the kernel tree, so it simply doesn't matter."

This isn't just a function or two being removed but amounts to 1,280 lines of code now stripped out of the kernel that was used by the NVIDIA binary driver on POWER. The NVIDIA POWER support will now break on Linux 5.3 but hopefully NVIDIA will be able to come up with a timely solution to fix their driver on 5.3 and newer.