linux-kernel - Re: [PATCH 3/8] rust: pci: add {enable,disable}

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Message-ID: <20251121232833.GH233636@ziepe.ca>
Date: Fri, 21 Nov 2025 19:28:33 -0400
From: Jason Gunthorpe <jgg@...pe.ca>
To: Peter Colberg <pcolberg@...hat.com>
Cc: Danilo Krummrich <dakr@...nel.org>, 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>,
	Abdiel Janulgue <abdiel.janulgue@...il.com>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Robin Murphy <robin.murphy@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dave Ertman <david.m.ertman@...el.com>,
	Ira Weiny <ira.weiny@...el.com>, Leon Romanovsky <leon@...nel.org>,
	linux-pci@...r.kernel.org, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alexandre Courbot <acourbot@...dia.com>,
	Alistair Popple <apopple@...dia.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	John Hubbard <jhubbard@...dia.com>, Zhi Wang <zhiw@...dia.com>
Subject: Re: [PATCH 3/8] rust: pci: add {enable,disable}_sriov(), to control
 SR-IOV capability

On Wed, Nov 19, 2025 at 05:19:07PM -0500, Peter Colberg wrote:
> Add methods to enable and disable the Single Root I/O Virtualization
> (SR-IOV) capability for a PCI device. The wrapped C methods take care
> of validating whether the device is a Physical Function (PF), whether
> SR-IOV is currently disabled (or enabled), and whether the number of
> requested VFs does not exceed the total number of supported VFs.
> 
> Suggested-by: Danilo Krummrich <dakr@...nel.org>
> Signed-off-by: Peter Colberg <pcolberg@...hat.com>
> ---
>  rust/kernel/pci.rs | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 814990d386708fe2ac652ccaa674c10a6cf390cb..556a01ed9bc3b1300a3340a3d2383e08ceacbfe5 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -454,6 +454,36 @@ pub fn set_master(&self) {
>          // SAFETY: `self.as_raw` is guaranteed to be a pointer to a valid `struct pci_dev`.
>          unsafe { bindings::pci_set_master(self.as_raw()) };
>      }
> +
> +    /// Enable the Single Root I/O Virtualization (SR-IOV) capability for this device,
> +    /// where `nr_virtfn` is number of Virtual Functions (VF) to enable.
> +    #[cfg(CONFIG_PCI_IOV)]
> +    pub fn enable_sriov(&self, nr_virtfn: i32) -> Result {
> +        // SAFETY:
> +        // `self.as_raw` returns a valid pointer to a `struct pci_dev`.
> +        //
> +        // `pci_enable_sriov()` checks that the enable operation is valid:
> +        // - the device is a Physical Function (PF),
> +        // - SR-IOV is currently disabled, and
> +        // - `nr_virtfn` does not exceed the total number of supported VFs.
> +        let ret = unsafe { bindings::pci_enable_sriov(self.as_raw(), nr_virtfn) };
> +        if ret != 0 {
> +            return Err(crate::error::Error::from_errno(ret));
> +        }
> +        Ok(())
> +    }
> +
> +    /// Disable the Single Root I/O Virtualization (SR-IOV) capability for this device.
> +    #[cfg(CONFIG_PCI_IOV)]
> +    pub fn disable_sriov(&self) {
> +        // SAFETY:
> +        // `self.as_raw` returns a valid pointer to a `struct pci_dev`.
> +        //
> +        // `pci_disable_sriov()` checks that the disable operation is valid:
> +        // - the device is a Physical Function (PF), and
> +        // - SR-IOV is currently enabled.
> +        unsafe { bindings::pci_disable_sriov(self.as_raw()) };
> +    }

Both these functions should only be called on bound devices - the
safety statement should call it out, does the code require it?

Also per my other email SRIOV should be disabled before a driver can
be unbound, this patch should take care of it to not introduce an
dangerous enable_sriov().

Jason