The Blackwell GSP Firmware That Wasn't Missing: A Debugging Epiphany

Message Overview

The subject message (index 550) is a turning point in a protracted debugging session aimed at deploying the GLM-5-NVFP4 large language model across eight NVIDIA RTX PRO 6000 Blackwell GPUs on a Proxmox VE host. For several rounds, the team had been stuck on a critical blocker: cuInit() — the CUDA runtime initialization call — was hanging indefinitely, returning exit code 124 (killed by timeout) rather than succeeding or even returning a clean error code. The prevailing hypothesis, articulated in the immediately preceding message ([msg 549]), was that the NVIDIA 590.48.01 open kernel module was failing to load GSP (GPU System Processor) firmware for the new Blackwell architecture, because the firmware directory at /lib/firmware/nvidia/590.48.01/ contained only two files — gsp_ga10x.bin and gsp_tu10x.bin — and no files with a gb* prefix that would indicate Blackwell support. The assistant had even begun planning a kernel upgrade from Proxmox's 6.8.12-9 to 6.8.12-18 as a potential fix.

Message 550 shatters that hypothesis with two simple but decisive commands. It is a textbook example of the scientific method in systems debugging: form a hypothesis, then design an experiment that can falsify it.

The Message, Quoted

[assistant] This is very informative. The firmware directory lists chips up to `ad102` (Ada Lovelace / RTX 4000 series) — **no Blackwell (`gb*`) firmware at all**. However, the driver is 590.48.01 which should support Blackwell. Let me look more carefully at the firmware structure and check the GSP firmware version the GPUs are reporting.
[bash] ssh root@10.1.2.6 "nvidia-smi -q 2>/dev/null | grep -A5 'GSP\|Firmware\|VBIOS' | head -30"
    VBIOS Version                                      : 98.02.67.00.0A
    MultiGPU Board                                     : No
    Board ID                                           : 0x100
    Board Part Number                                  : 900-2G153-0000-000
    GPU Part Number                                    : 2BB5-895-A1
    FRU Part Number                                    : N/A
--
    GSP Firmware Version                               : 590.48.01
    IBMNPU
        Relaxed Or...
[bash] ssh root@10.1.2.6 "ls /lib/firmware/nvidia/590.48.01/; echo '---'; file /lib/firmware/nvidia/590.48.01/gsp_ga10x.bin; echo '---'; strings /lib/firmware/nvidia/590.48.01/gsp_ga10x.bin | grep -i 'blackwell\|gb20\|sm120\|sm12' | head -5"
gsp_ga10x.bin
gsp_tu10x.bin
---
/lib/firmware/nvidia/590.48.01/gsp_ga10x.bin: ELF 64-bit LSB relocatable, UCB RISC-V, soft-float ABI, version 1 (SYSV), BuildID[sha1]=cf812cb3f2f1e8c8209dc2e446fdf536ba9ec88f, not stripped
---
kernel_gb20y.elf
kernel_gb20x.elf
kernel_gb20x.elf
kernel_gb20y.elf
.fwsignature_gb20y

Why This Message Was Written: The Reasoning and Motivation

The assistant was operating under a specific, well-reasoned hypothesis: that the cuInit() hang was caused by missing GSP firmware for Blackwell GPUs. This hypothesis had strong surface-level evidence. The firmware directory listing showed only two files, neither with a Blackwell-sounding name. The assistant had searched the entire filesystem for any gsp_gb* or gsp_bb* files and found none. The Proxmox kernel (6.8.12-9) was several versions behind the available 6.8.12-18. And the NVIDIA open kernel module's documentation indicated that GSP firmware loading was a prerequisite for GPU initialization with the open-source driver stack.

However, the assistant's reasoning in message 550 reveals a crucial intellectual pivot: "However, the driver is 590.48.01 which should support Blackwell." This single sentence is the seed of doubt that drives the entire message. The assistant recognizes a contradiction between the hypothesis (missing firmware) and the known facts (the driver version 590.48.01 was explicitly released to support Blackwell). Rather than doubling down on the kernel-upgrade plan, the assistant decides to "look more carefully at the firmware structure and check the GSP firmware version the GPUs are reporting."

This is the hallmark of a skilled debugger: when the evidence supports a hypothesis but the hypothesis conflicts with a known invariant, you re-examine the evidence at a deeper level rather than assuming the invariant is wrong.

How Decisions Were Made

Two key investigative decisions are visible in this message:

Decision 1: Query the GPU's reported GSP firmware version via nvidia-smi -q. This is a clever move because it bypasses the filesystem entirely. Instead of asking "what firmware files exist on disk," the assistant asks "what firmware version does the GPU report it has loaded." The GPU's VBIOS and GSP firmware version are stored in the card's own firmware flash; nvidia-smi -q reads these directly from the hardware registers. If the GPU reports a GSP firmware version, then firmware has been loaded, regardless of what the filesystem looks like. The result — "GSP Firmware Version: 590.48.01" — is the first crack in the missing-firmware hypothesis.

Decision 2: Inspect the actual binary contents of gsp_ga10x.bin. Rather than relying on filenames, the assistant uses file to confirm it's an ELF binary, then strings to grep for Blackwell-specific identifiers. This reveals that gsp_ga10x.bin is a multi-architecture firmware bundle containing ELF sections for gb20x and gb20y — the Blackwell GPU die variants. The "ga10x" in the filename refers to the container format (a legacy naming convention from the Ampere architecture), not the contents. The firmware bundle is a superset that includes firmware for multiple GPU generations, and Blackwell support is embedded inside it.

Assumptions Made and Mistakes Corrected

The assistant made several implicit assumptions that this message corrects:

Assumption 1: Firmware filenames indicate architecture support. This was the most consequential assumption. The team had searched for gsp_gb* files and concluded Blackwell firmware didn't exist. But NVIDIA's firmware packaging strategy uses a single "ga10x" bundle that contains firmware for all supported architectures from Ampere through Blackwell. The filename is a historical artifact, not a content descriptor.

Assumption 2: The cuInit() hang is a firmware loading issue. This was a reasonable inference from the symptoms, but message 550 disproves it. If GSP firmware is loaded and the GPU reports version 590.48.01, then the hang must have a different root cause — perhaps a kernel module parameter, a cgroup/namespace restriction, or an IOMMU interaction.

Assumption 3: The Proxmox kernel is too old for the NVIDIA driver. While the kernel upgrade may still be beneficial, the firmware discovery removes it as the primary suspect for the cuInit() hang. The driver and firmware are actually functioning correctly at the GSP level.

The message does not contain obvious new mistakes, but it does reveal a prior mistake: the team had spent significant effort searching for Blackwell firmware files by name, when the firmware was already present and loaded. This is a classic "looking in the wrong place" error.

Input Knowledge Required

To fully understand this message, a reader needs:

  1. Understanding of GPU firmware architecture: Knowledge that modern NVIDIA GPUs have a GSP (GPU System Processor) — a RISC-V coprocessor that handles GPU initialization, power management, and scheduling. The GSP runs its own firmware, which the kernel driver loads from /lib/firmware/nvidia/.
  2. Familiarity with NVIDIA's firmware naming conventions: The "ga10x" name refers to the GA10x GPU family (Ampere/RTX 3000 series), but NVIDIA bundles firmware for multiple architectures into a single binary. The strings output showing kernel_gb20x.elf indicates that the binary contains ELF payloads for Blackwell (gb20x/gb20y).
  3. Knowledge of the debugging context: The preceding messages established that cuInit() hangs with exit code 124, that the firmware directory appears to lack Blackwell files, and that the team was considering a kernel upgrade.
  4. Familiarity with Proxmox VE: Understanding that Proxmox runs a custom kernel (6.8.12-9-pve) and that kernel upgrades are managed through proxmox-boot-tool.
  5. Understanding of the nvidia-smi -q query interface: Knowing that -q dumps all GPU properties, and that grepping for "GSP" reveals the firmware version loaded on the card.

Output Knowledge Created

This message produces several critical pieces of knowledge:

  1. The GSP firmware is loaded and operational. The GPU reports "GSP Firmware Version: 590.48.01," confirming that the driver successfully loaded firmware onto the Blackwell GPUs' GSP coprocessors.
  2. Blackwell firmware exists inside the gsp_ga10x.bin bundle. The strings output reveals kernel_gb20x.elf and kernel_gb20y.elf — the actual RISC-V firmware binaries for Blackwell's two die variants (GB20X and GB20Y). The .fwsignature_gb20y entry confirms NVIDIA cryptographically signs the Blackwell firmware payloads.
  3. The cuInit() hang has a different root cause. Since firmware loading is not the problem, the investigation must pivot to other potential causes: kernel module parameters (e.g., nvidia_uvm's HMM feature, which was later discovered to be the culprit), IOMMU configuration, or cgroup device restrictions.
  4. The gsp_ga10x.bin file is a multi-architecture bundle. It's an ELF binary containing RISC-V relocatable object files for multiple GPU generations. The file command identifies it as "ELF 64-bit LSB relocatable, UCB RISC-V, soft-float ABI" — confirming the GSP uses a RISC-V core.

The Thinking Process Visible in the Message

The assistant's reasoning unfolds in three clear stages within this message:

Stage 1 — Re-evaluation of the hypothesis: The message opens with a summary of what was known ("firmware directory lists chips up to ad102 — no Blackwell firmware at all") immediately qualified by a contradiction ("However, the driver is 590.48.01 which should support Blackwell"). This "however" is the critical reasoning step. The assistant is weighing two pieces of evidence: the filesystem evidence (no gb* files) against the version evidence (driver 590 supports Blackwell). Rather than accepting the filesystem evidence at face value, the assistant decides to investigate deeper.

Stage 2 — Direct hardware interrogation: The assistant chooses to query the GPU directly via nvidia-smi -q. This is a classic debugging tactic: when the OS/filesystem view is ambiguous, ask the hardware directly. The GPU reports GSP Firmware Version 590.48.01, proving that firmware was loaded. This is the falsification of the hypothesis.

Stage 3 — Binary forensic analysis: Having discovered that firmware is loaded, the assistant now needs to understand how — because the filesystem still shows no gb files. The strings command on gsp_ga10x.bin reveals the answer: the Blackwell firmware is embedded inside the "ga10x" bundle. The assistant doesn't stop at "firmware is loaded"; they dig into why* the earlier filename-based search was misleading. This thoroughness prevents the same mistake from recurring.

The thinking is methodical, hypothesis-driven, and self-correcting. The assistant treats their own prior conclusion ("no Blackwell firmware") as a hypothesis to be tested, not a fact to be acted upon.

Broader Significance

This message is a microcosm of what makes effective systems debugging: the willingness to question one's own assumptions, the creativity to design experiments that can falsify a hypothesis, and the thoroughness to understand why evidence was misleading, not just that it was wrong. The discovery that gsp_ga10x.bin is a multi-architecture firmware bundle saved the team from an unnecessary kernel upgrade and redirected their attention to the real culprit — the nvidia_uvm module's Heterogeneous Memory Management (HMM) feature, which was incompatible with the Proxmox kernel and caused cuInit() to hang. In the subsequent message ([msg 551]), the assistant explicitly notes: "So the issue is NOT missing firmware. GSP is loaded and running. The hang in cuInit() must be something else entirely." This pivot, enabled by the discoveries in message 550, ultimately led to the fix: setting uvm_disable_hmm=1 as a module parameter.

The message also serves as a cautionary tale about naming conventions in complex systems. The filename gsp_ga10x.bin was inherited from the Ampere generation and never updated to reflect its expanded contents. Engineers who relied on filename-based searches would repeatedly miss the Blackwell firmware embedded within. Only by inspecting the binary's actual contents — using strings to search for architecture identifiers — could the truth be uncovered. This is a reminder that in systems debugging, the filesystem is a model of reality, not reality itself.