Re: [PATCH v9 2/2] selftests/vfio: Add NVIDIA Falcon driver for DMA testing

[David Matlack <dmatlack@google.com>]

On 2026-03-17 02:42 PM, Rubin Du wrote:
> Add a new VFIO PCI driver for NVIDIA GPUs that enables DMA testing
> via the Falcon (Fast Logic Controller) microcontrollers. This driver
> extracts and adapts the DMA test functionality from the NVIDIA
> gpu-admin-tools project and integrates it into the existing VFIO
> selftest framework.
> 
> The Falcon is a general-purpose microcontroller present on NVIDIA GPUs
> that can perform DMA operations between system memory and device memory.
> By leveraging Falcon DMA, this driver allows NVIDIA GPUs to be tested
> alongside Intel IOAT and DSA devices using the same selftest infrastructure.
> 
> Supported GPUs:
> - Kepler: K520, GTX660, K4000, K80, GT635
> - Maxwell Gen1: GTX750, GTX745
> - Maxwell Gen2: M60
> - Pascal: P100, P4, P40
> - Volta: V100
> - Turing: T4
> - Ampere: A16, A100, A10
> - Ada: L4, L40S
> - Hopper: H100
> 
> The PMU falcon on Kepler and Maxwell Gen1 GPUs uses legacy FBIF register
> offsets and requires enabling via PMC_ENABLE with the HUB bit set.
> 
> Limitations and tradeoffs:
> 
> 1. Architecture support:
>    Blackwell and newer architectures may require additional work
>    due to firmware.
> 
> 2. Synchronous DMA operations:
>    Each transfer blocks until completion because the reference
>    implementation does not expose command queuing - only one
>    DMA operation can be in flight at a time.

Asynchronous DMA will be important for testing Live Update:

  https://lore.kernel.org/kvm/20260129212510.967611-23-dmatlack@google.com/

That is why I split memcpy_start() and memcpy_wait() from the beginning.

Would it be possible to add support for it here even though it is not in
the reference implementation?

> 
> The driver is named 'nv_falcon' to reflect that it specifically controls
> the Falcon microcontroller for DMA operations, rather than exposing
> general GPU functionality.
> 
> Reference implementation:
> https://github.com/NVIDIA/gpu-admin-tools
> 
> Signed-off-by: Rubin Du <rubind@nvidia.com>