linux-kernel - Re: [PATCH 1/2] rust: pci: add is

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Message-ID: <zqogmf4mnadxkthhzyfhzesk3pdafnr7jqf5i22ahkdo5ugt63@gvb5xhgjylku>
Date: Wed, 1 Oct 2025 10:30:43 +1000
From: Alistair Popple <apopple@...dia.com>
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>, Zhi Wang <zhiw@...dia.com>, Surath Mitra <smitra@...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 1/2] rust: pci: add is_virtfn(), to check for VFs

On 2025-10-01 at 08:07 +1000, John Hubbard <jhubbard@...dia.com> wrote...
> Add a method to check if a PCI device is a Virtual Function (VF). This
> allows Rust drivers to determine whether a device is a VF created
> through SR-IOV. This is required in order to implement VFIO, because
> drivers such as NovaCore must only bind to Physical Functions (PFs) or
> regular PCI devices. The VFs must be left unclaimed, so that a VFIO
> kernel module can claim them.
> 
> is_virtfn() returns true if the device's is_virtfn flag is set, matching
> the behavior of the C code.

Seems fine to me so please add:

Reviewed-by: Alistair Popple <apopple@...dia.com>

> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
>  rust/kernel/pci.rs | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 7fcc5f6022c1..476b80f05905 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -496,6 +496,12 @@ pub fn resource_start(&self, bar: u32) -> Result<bindings::resource_size_t> {
>          Ok(unsafe { bindings::pci_resource_start(self.as_raw(), bar.try_into()?) })
>      }
>  
> +    /// Returns true if this device is a Virtual Function (VF).
> +    pub fn is_virtfn(&self) -> bool {
> +        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
> +        unsafe { (*self.as_raw()).is_virtfn() != 0 }
> +    }
> +
>      /// Returns the size of the given PCI bar resource.
>      pub fn resource_len(&self, bar: u32) -> Result<bindings::resource_size_t> {
>          if !Bar::index_is_valid(bar) {
> -- 
> 2.51.0
>