linux-kernel - Re: [PATCH v2 2/3] gpu: nova-core: avoid probing non-display/compute PCI functions

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Message-ID: <aKVGFC4UVpjyAXWO@archiso>
Date: Wed, 20 Aug 2025 03:50:44 +0000
From: Elle Rhumsaa <elle@...thered-steel.dev>
To: John Hubbard <jhubbard@...dia.com>
Cc: Danilo Krummrich <dakr@...nel.org>,
	Alexandre Courbot <acourbot@...dia.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Timur Tabi <ttabi@...dia.com>, Alistair Popple <apopple@...dia.com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	nouveau@...ts.freedesktop.org, linux-pci@...r.kernel.org,
	rust-for-linux@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] gpu: nova-core: avoid probing non-display/compute
 PCI functions

On Sun, Aug 17, 2025 at 06:33:04PM -0700, John Hubbard wrote:
> NovaCore has so far been too imprecise about figuring out if .probe()
> has found a supported PCI PF (Physical Function). By that I mean:
> .probe() sets up BAR0 (which involves a lot of very careful devres and
> Device<Bound> details behind the scenes). And then if it is dealing with
> a non-supported device such as the .1 audio PF on many GPUs, it fails
> out due to an unexpected BAR0 size. We have been fortunate that the BAR0
> sizes are different.
> 
> Really, we should be filtering on PCI class ID instead. These days I
> think we can confidently pick out Nova's supported PF's via PCI class
> ID. And if not, then we'll revisit.
> 
> The approach here is to filter on "Display VGA" or "Display 3D", which
> is how PCI class IDs express "this is a modern GPU's PF".
> 
> Cc: Danilo Krummrich <dakr@...nel.org>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
>  drivers/gpu/nova-core/driver.rs | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
> index 274989ea1fb4..4ec5b861a345 100644
> --- a/drivers/gpu/nova-core/driver.rs
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -1,6 +1,8 @@
>  // SPDX-License-Identifier: GPL-2.0
>  
> -use kernel::{auxiliary, bindings, c_str, device::Core, pci, prelude::*, sizes::SZ_16M, sync::Arc};
> +use kernel::{
> +    auxiliary, bindings, c_str, device::Core, pci, pci::Class, prelude::*, sizes::SZ_16M, sync::Arc,
> +};
>  
>  use crate::gpu::Gpu;
>  
> @@ -18,10 +20,25 @@ pub(crate) struct NovaCore {
>      PCI_TABLE,
>      MODULE_PCI_TABLE,
>      <NovaCore as pci::Driver>::IdInfo,
> -    [(
> -        pci::DeviceId::from_id(bindings::PCI_VENDOR_ID_NVIDIA, bindings::PCI_ANY_ID as u32),
> -        ()
> -    )]
> +    [
> +        // Modern NVIDIA GPUs will show up as either VGA or 3D controllers.
> +        (
> +            pci::DeviceId::from_class_and_vendor(
> +                Class::DISPLAY_VGA,
> +                Class::MASK_CLASS_SUBCLASS,
> +                bindings::PCI_VENDOR_ID_NVIDIA
> +            ),
> +            ()
> +        ),
> +        (
> +            pci::DeviceId::from_class_and_vendor(
> +                Class::DISPLAY_3D,
> +                Class::MASK_CLASS_SUBCLASS,
> +                bindings::PCI_VENDOR_ID_NVIDIA
> +            ),
> +            ()
> +        ),
> +    ]
>  );
>  
>  impl pci::Driver for NovaCore {
> -- 
> 2.50.1

Reviewed-by: Elle Rhumsaa <elle@...thered-steel.dev>