The Missing Firmware: Diagnosing CUDA Initialization Failure on Blackwell GPUs with Proxmox

Introduction

In the complex dance between hardware, kernel modules, and GPU firmware, sometimes the most revealing clue is an absence. Message 536 of this opencode session captures a pivotal diagnostic moment: the assistant notices that no GSP (GPU System Processor) firmware loading messages appear in the kernel log, and investigates whether the NVIDIA driver package contains the right firmware files for the Blackwell-generation RTX PRO 6000 GPUs. This single observation—what isn't happening—becomes the critical thread in unraveling why CUDA refuses to initialize on a Proxmox host despite the driver appearing to load correctly.

The Context: A Migration Gone Wrong

To understand the weight of this message, one must appreciate the journey that led here. The session had been working toward deploying the GLM-5-NVFP4 model—a massive 744B-parameter MoE language model—across 8 NVIDIA RTX PRO 6000 Blackwell Server Edition GPUs. The initial deployment inside a KVM virtual machine had achieved respectable throughput (~485 tok/s) but was fundamentally bottlenecked by GPU-to-GPU communication latency. The root cause was the VFIO/IOMMU virtualization layer: because each GPU sat in its own IOMMU group, the PCIe P2P (Peer-to-Peer) DMA that normally allows GPUs to communicate directly was impossible. Every cross-GPU transfer had to bounce through system memory, adding a ~13µs floor to latency.

The team's solution was bold: abandon the KVM VM entirely and migrate the GPU workload to an LXC container on the Proxmox host. LXC containers share the host kernel but present a near-bare-metal device interface, meaning the GPUs would see each other as directly connected peers. The topology inside the container confirmed this—nvidia-smi topo -m showed NODE within sockets and SYS across sockets, the true bare-metal topology, instead of the PHB (PCIe Host Bridge) topology that had plagued the VM. It was a clean win.

But then everything stopped.

The Blocker: CUDA Error Code 3

Despite nvidia-smi happily reporting all 8 GPUs—their temperatures, power draw, PCIe bus locations, everything—the CUDA runtime refused to initialize. A simple cuInit(0) call returned error code 3, CUDA_ERROR_NOT_INITIALIZED. This failure occurred on both the Proxmox host and inside the LXC container, ruling out container-specific issues like missing device nodes or cgroup restrictions.

The assistant had already run an exhaustive battery of diagnostics across the preceding messages (see [msg 515] through [msg 535]). It had confirmed that the device nodes were correctly bind-mounted, the minor numbers matched, the /proc/driver/nvidia/gpus/ entries were populated with proper GPU UUIDs and firmware versions, and even low-level C code using dlopen on libcuda.so returned the same error. It had tried both the open-source kernel module (which saw the GPUs but couldn't initialize CUDA) and the proprietary kernel module (which couldn't see the GPUs at all). It had reinstalled the driver, reloaded modules, and checked dmesg for errors—finding none.

This is the state of affairs as message 536 begins: the assistant has exhausted the obvious checks and is now looking for something more subtle.

The Observation: Silence in the Logs

The message opens with a sharp observation:

I notice there's no GSP firmware loading message — it should show loading gsp_*.bin. On Blackwell GPUs, the open module requires GSP firmware.

This is the kind of insight that comes from deep familiarity with NVIDIA's driver architecture. The GSP (GPU System Processor) is a dedicated microcontroller embedded in modern NVIDIA GPUs that handles low-level tasks like power management, PCIe negotiation, and—crucially—firmware initialization. Starting with the Turing architecture (RTX 20-series), NVIDIA moved more of the GPU initialization logic into GSP firmware blobs that the kernel module loads at startup. When the open kernel module initializes a GPU, it should log messages like "loading GSP firmware" as it transfers the firmware binary to the GPU's GSP. The complete absence of such messages in dmesg suggests the firmware loading step is either being skipped or failing silently.

The assistant then runs a targeted command to check the firmware files:

ls -la /lib/firmware/nvidia/590.48.01/
find /lib/firmware/nvidia -name "*.bin" 2>/dev/null
nvidia-smi --query-gpu=name,compute_cap --format=csv
lspci -nn -s 01:00.0

The output is damning. The firmware directory contains exactly two files:

The Assumption and Its Nuance

The assistant's immediate conclusion is reasonable: the driver lacks Blackwell GSP firmware, and that's why CUDA initialization fails. But the follow-up message ([msg 537]) reveals an important complication:

Wait — in the KVM VM, this same driver version works with CUDA. The difference is the VM has its own driver directly accessing VFIO-passed GPUs. Here the open kernel module is loaded but the GSP firmware for Blackwell may be embedded in the kernel module itself rather than a separate file.

This is a critical refinement. The same driver version (590.48.01) works perfectly inside the KVM VM, where the guest operating system runs its own instance of the NVIDIA kernel module compiled against Ubuntu's kernel headers. If the missing firmware files were the sole cause, the VM would also fail—but it doesn't. This suggests either:

  1. The GSP firmware for Blackwell is embedded within the kernel module binary (nvidia.ko) rather than distributed as a separate .bin file, and the open module's initialization path differs between native and VFIO-passed devices.
  2. The Proxmox host kernel (6.8.12-9-pve) is missing patches that the Ubuntu 24.04 kernel (6.8.0-100-generic) has, affecting how the open module interacts with Blackwell GPUs.
  3. The VFIO passthrough path bypasses GSP initialization entirely, delegating it to the guest's driver stack, while the native path requires the host to handle GSP firmware loading—and fails when it can't find the right blob. The assistant's thinking reveals a sophisticated understanding of the layered architecture. It recognizes that "the same driver version" is not actually the same software stack: the host and the VM run different kernels, different module builds, and potentially different initialization paths. The firmware files on disk are only part of the story.

Input Knowledge Required

To fully grasp this message, the reader needs several layers of context:

Hardware architecture knowledge: Understanding that modern NVIDIA GPUs contain a GSP coprocessor that must be loaded with firmware before the GPU is fully operational. This is analogous to how a modern CPU needs microcode updates, or how a network card needs firmware loaded before it can negotiate a link.

NVIDIA driver stack knowledge: The distinction between the open kernel module (nvidia-open) and the proprietary kernel module (nvidia), and the fact that Blackwell GPUs require the open module. The --print-recommended-kernel-module-type flag confirms this—the installer itself recommends open for these GPUs.

Proxmox-specific knowledge: The PVE kernel (6.8.12-9) is based on Ubuntu's 6.8 kernel but with Proxmox-specific patches for virtualization, ZFS, and container management. These patches may diverge from the mainline kernel in ways that affect GPU driver compatibility.

The session's history: The failed migration from KVM to LXC, the P2P bottleneck, the topology verification, and the earlier diagnostic steps that ruled out device node issues, cgroup restrictions, and module loading order.

Output Knowledge Created

This message produces several important insights:

  1. The driver package 590.48.01 does not contain Blackwell-specific GSP firmware as separate files. This is a concrete, verifiable fact. The firmware directory contains only gsp_ga10x.bin and gsp_tu10x.bin.
  2. GSP firmware loading is not occurring. The absence of GSP-related messages in dmesg, combined with the missing firmware files, suggests the initialization path is failing before or during firmware transfer.
  3. The diagnostic approach shifts from "what's wrong with the container" to "what's different about the host." Since the same driver works in the VM, the problem must be in the host environment—the kernel version, the module build, or the PCIe initialization path.
  4. A concrete next-step hypothesis emerges: the PVE kernel may be too old for the Blackwell open module. The assistant immediately checks the kernel version (6.8.12-9-pve) and finds that a newer PVE kernel (6.8.12-18) is available as an upgrade.

The Thinking Process

What makes this message particularly instructive is the reasoning structure. The assistant doesn't just run commands; it articulates a chain of inference:

  1. Observation: No GSP firmware loading messages in dmesg.
  2. Domain knowledge: Blackwell GPUs with the open module require GSP firmware.
  3. Hypothesis: The firmware files might be missing.
  4. Test: Check /lib/firmware/nvidia/590.48.01/.
  5. Result: Only Ampere and Turing firmware present.
  6. Refined hypothesis: The driver lacks Blackwell firmware → CUDA can't initialize. But then, in the very next breath ([msg 537]), the assistant catches itself with a counterexample: the VM works with the same driver. This forces a revision of the hypothesis. The assistant doesn't discard the firmware observation—it's still a real finding—but reframes it as part of a larger puzzle. The missing firmware files might be a symptom rather than the cause, pointing toward a kernel compatibility issue rather than a simple missing file. This self-correcting reasoning is characteristic of effective debugging. The assistant holds multiple hypotheses simultaneously, tests each one, and when evidence contradicts a hypothesis, it doesn't reject the evidence—it refines the hypothesis.

The Broader Significance

Message 536 sits at a critical juncture in the session. The team has invested enormous effort in the LXC migration—installing the NVIDIA driver on the Proxmox host (which required adding repositories, installing build tools, blacklisting Nouveau, and compiling the kernel module with DKMS), converting the container from unprivileged to privileged, configuring bind-mounts for all 8 GPUs, copying the 405GB model cache, and setting up the entire Python ML environment. The topology win (NODE/SYS instead of PHB) was supposed to be the payoff.

Now that payoff is blocked by a CUDA initialization failure that defies easy explanation. The GSP firmware observation is the first clue that points toward a root cause beyond the container configuration—something fundamental about the host kernel's compatibility with Blackwell GPUs. It shifts the investigation from "what did we misconfigure" to "what does the host kernel lack."

The message also illustrates a principle of debugging complex systems: when everything that should be happening isn't happening, pay attention to the silences. The absence of GSP firmware loading messages, buried in the noise of dmesg output, becomes the key signal. It's not what the logs say that matters—it's what they don't say.

Conclusion

Message 536 is a masterclass in diagnostic reasoning under uncertainty. The assistant identifies a concrete anomaly (missing GSP firmware loading), verifies it with targeted commands, and produces a falsifiable finding (no Blackwell GSP firmware files in the driver package). But rather than stopping at this surface-level conclusion, the assistant immediately contextualizes it against the counterexample of the working KVM VM, leading to a more nuanced hypothesis about kernel compatibility. This self-correcting loop—observe, hypothesize, test, refine—is the essence of effective technical debugging, and this message captures it in miniature.