The Silent Reset: Chasing Blackwell GSP Firmware Corruption Through NVIDIA's GPU Admin Tools

In the long arc of debugging a complex GPU infrastructure problem, some messages are decisive breakthroughs and others are quiet pivots that reveal as much about the problem's nature as any successful fix. Message [msg 6297] belongs firmly to the latter category. It is a transitional message — brief, almost perfunctory — in which the assistant, having exhausted one approach, pivots to another tool in the NVIDIA GPU admin toolkit, only to set the stage for yet another dead end. But within this small message lies a rich story about the nature of GPU firmware, the limits of software-initiated resets on Blackwell architecture, and the disciplined methodology required to systematically eliminate possibilities.

The Message in Full

The assistant writes:

It returned silently. Let me also try --set-next-sbr-to-fundamental-reset followed by --reset-with-sbr:

>

``bash ssh root@10.1.2.6 'echo "=== Unload nvidia ===" && rmmod nvidia_drm 2>/dev/null; rmmod nvidia_uvm 2>/dev/null; rmmod nvidia_modeset 2>/dev/null; rmmod nvidia 2>/dev/null && echo "unloaded" && lsmod | grep nvidia || echo "clean"' ``

>

`` === Unload nvidia === unloaded clean ``

The message is composed of two parts: a brief reasoning sentence and a bash command with its output. The command is straightforward — it unloads all four NVIDIA kernel modules (nvidia_drm, nvidia_uvm, nvidia_modeset, nvidia) and verifies the unload succeeded. The output confirms "unloaded" and "clean," meaning no nvidia modules remain in memory.

The Context: A Multi-Message Reset Campaign

To understand why this message exists at all, we must trace the thread that leads to it. The assistant has been engaged in an increasingly desperate campaign to restore P2P DMA functionality across four NVIDIA RTX PRO 6000 Blackwell GPUs on a Proxmox host. The root cause is an IOMMU configuration problem: under the SEV-SNP (Secure Encrypted Virtualization-Secure Nested Paging) IOMMU mode required for the host's confidential computing VM, GPU peer-to-peer DMA transactions corrupt data. The standard workaround — disabling P2P via NCCL_P2P_DISABLE=1 — works but sacrifices performance.

The assistant's strategy has been to set individual IOMMU groups to "identity" mode, which bypasses DMA translation and should theoretically allow clean P2P transfers. This approach worked in earlier sessions on different hardware, but on Blackwell GPUs it has run into a fundamental obstacle: the GPU's Firmware Security Processor (FSP), also referred to as the GSP (GPU System Processor), fails to initialize when IOMMU is in identity mode.

In the messages immediately preceding [msg 6297], the assistant has been trying various reset methods to clear the corrupted GSP state. Message [msg 6290] attempted a full cycle of unloading nvidia, removing GPUs from the PCI bus, issuing Secondary Bus Reset (SBR) on the upstream bridges, and rescanning — all while identity domains were set. The result was "No devices were found" and dmesg errors showing RmInitAdapter failed with error code 0x62:0xffff:2142 and Cannot initialize GSP firmware RM.

Message [msg 6294] recognized the deeper nature of the problem: "The FSP firmware lives in protected on-chip SRAM and survives software-initiated resets." This was a critical insight — standard SBR cannot clear the FSP state because the firmware is stored in memory that persists across conventional PCI resets.

This led the assistant to discover nvidia_gpu_tools.py in /opt/gpu-admin-tools/ ([msg 6295]), an NVIDIA GPU administration utility with options like --recover-broken-gpu, --reset-with-sbr, and --set-next-sbr-to-fundamental-reset. In [msg 6296], the assistant tried --recover-broken-gpu on GPU 01:00.0, which produced only an INFO line about selecting the GPU and then... nothing. It returned silently.

The Reasoning: Interpreting Silence

The opening line of [msg 6297] — "It returned silently" — is the key reasoning artifact. The assistant is interpreting the lack of error output from --recover-broken-gpu as inconclusive. The tool produced no success message, no failure message, no indication of what it actually did. In the world of systems debugging, silent returns from diagnostic tools are ambiguous: they could mean the operation succeeded without fanfare, or they could mean the tool attempted something and failed without reporting it, or they could mean the tool doesn't actually support the operation on this hardware.

The assistant's decision to move on rather than dig deeper into the --recover-broken-gpu result is a pragmatic choice. Given that the GPUs still fail after this operation (as subsequent messages confirm), the silence was likely an indication that the tool couldn't perform the recovery on Blackwell hardware. Rather than waste time trying to extract more verbose logging from a tool that may simply not support this GPU generation, the assistant pivots to a different flag combination: --set-next-sbr-to-fundamental-reset followed by --reset-with-sbr.

This two-step approach is interesting. --set-next-sbr-to-fundamental-reset presumably writes a register that tells the GPU to treat the next SBR as a fundamental reset (deeper than a conventional secondary bus reset — possibly equivalent to a PCIe hot reset or a function-level reset that reaches the firmware). Then --reset-with-sbr triggers that reset. The assistant's reasoning is: if the FSP state survives a normal SBR, perhaps a fundamental reset can clear it.

The Assumptions at Play

Several assumptions underpin this message:

Assumption 1: The fundamental reset mechanism is supported on Blackwell GPUs. This is a significant assumption. The --set-next-sbr-to-fundamental-reset flag may only work on certain GPU architectures (e.g., Hopper or older). Blackwell (GB100/GB200) is a new architecture, and the GPU admin tools may not yet have full support for it. The subsequent message ([msg 6298]) reveals this assumption was wrong — the tool returned an ERROR when trying to set the fundamental reset flag.

Assumption 2: The nvidia modules must be unloaded before the reset. This is correct — you cannot reset a device while its driver is actively managing it. The assistant correctly unloads all four modules in dependency order (drm → uvm → modeset → nvidia) and verifies the unload.

Assumption 3: The fundamental reset, if supported, would clear the FSP state. This is a reasonable assumption based on how PCIe fundamental resets work — they should reinitialize the device from a more initial state than a secondary bus reset. However, the subsequent failure to even set the flag makes this assumption untestable.

Assumption 4: The silent return from --recover-broken-gpu was not a success. The assistant implicitly assumes that if the recovery had worked, the GPUs would now be functional. Since they're not, the silent return is interpreted as a failure. This is a reasonable inference but not proven — it's possible the recovery did something but the identity IOMMU mode independently prevents the GPU from initializing.

The Input Knowledge Required

To fully understand this message, the reader needs knowledge of:

  1. The NVIDIA GPU driver stack: That nvidia, nvidia_modeset, nvidia_uvm, and nvidia_drm are four separate kernel modules that must be loaded in a specific order and unloaded in reverse order. The rmmod commands with 2>/dev/null suppress errors from modules that are already unloaded.
  2. PCIe reset types: The distinction between Secondary Bus Reset (SBR), which is a conventional PCIe hot reset propagated across a bridge, and Fundamental Reset, which is a deeper reset that reinitializes the device's configuration space and internal state. The FSP/GSP firmware on Blackwell GPUs survives SBR but might not survive a fundamental reset.
  3. IOMMU modes: The difference between "DMA-FQ" (translation mode, the default) and "identity" mode (passthrough, bypassing translation). The assistant is trying to use identity mode to avoid the DMA remapping issues that corrupt P2P traffic under SEV-SNP.
  4. The Blackwell FSP architecture: That Blackwell GPUs have a dedicated Firmware Security Processor that manages GPU initialization, and that this processor's firmware lives in protected on-chip SRAM that persists across conventional resets. This is a new feature of the Blackwell architecture that complicates reset recovery.
  5. The nvidia_gpu_tools.py utility: An NVIDIA tool for GPU administration that provides hardware-level reset capabilities beyond what nvidia-smi offers.

The Output Knowledge Created

This message produces several pieces of knowledge:

  1. Confirmation that nvidia modules can be cleanly unloaded: The output "unloaded / clean" confirms that all four modules are removed from kernel memory. This is important because subsequent operations (like setting identity domains or issuing resets) require the GPU to be driverless.
  2. A documented attempt to use --set-next-sbr-to-fundamental-reset: The message sets up the experiment, and the follow-up message ([msg 6298]) will document its failure. This creates a chain of evidence that fundamental reset is not supported on these Blackwell GPUs.
  3. A pattern of methodical elimination: The assistant is systematically working through the available reset mechanisms: manual SBR (tried in [msg 6290]), --recover-broken-gpu (tried in [msg 6296], returned silently), and now the fundamental reset path. Each elimination narrows the space of possible solutions.

The Thinking Process Visible in the Reasoning

The brief reasoning line — "It returned silently. Let me also try..." — reveals a specific cognitive process. The assistant is treating the silent return as a data point but not a conclusive one. Rather than spending time investigating why --recover-broken-gpu produced no output (e.g., by adding --log debug or checking return codes), the assistant makes a cost-benefit decision: there's another flag combination available, and trying it is faster than debugging the previous tool's output.

This is characteristic of experienced systems debugging: when a tool fails silently, the fastest path to information is often to try the next tool rather than to instrument the first one. The assistant is building a differential diagnosis — if --recover-broken-gpu didn't work and --set-next-sbr-to-fundamental-reset also doesn't work, that tells us something about the hardware's reset capabilities regardless of why each individual tool failed.

The choice to unload nvidia modules before setting the fundamental reset flag is also telling. The assistant could have set the flag while the driver was loaded (using --ignore-nvidia-driver as seen in later messages), but chooses to unload first. This suggests a conservative approach: ensure the device is in a quiescent state before attempting hardware-level operations.

The Broader Significance

Message [msg 6297] sits at a pivot point in a larger narrative about the limits of software GPU reset on Blackwell architecture. The assistant will eventually discover (in [msg 6300] and [msg 6301]) that even the gpu-admin-tools resets cannot clear the FSP corruption, and will ultimately conclude that "per-group IOMMU identity domains are fundamentally incompatible with Blackwell GPUs" (as the segment summary puts it). The FSP's requirement for specific DMA mappings set up by the kernel's DMA API in translation mode means that identity mode breaks GPU initialization at a hardware level that no software reset can fix.

This message, then, is one of the final steps in ruling out the software-reset approach. The assistant tries the deepest reset available in the NVIDIA tooling, and when it fails, the remaining path is clear: either find a way to make DmaRemapPeerMmio=1 work correctly (which is already enabled but produces incomplete IOMMU mappings), or accept that P2P DMA cannot be restored on this hardware configuration. The message is small, but it carries the weight of a narrowing possibility space — each silent return and each unsupported flag brings the investigation closer to its final conclusion.