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Date: Wed, 30 Sep 2026 16:25:36 +0200
Message-Id: <DLSPXUPSF0TC.3PC9F8RTDV1IL@kernel.org>
Subject: Re: [PATCH v3 08/10] rust: pci: add SR-IOV enable and disable
 tokens
Cc: <rust-for-linux@vger.kernel.org>, <linux-pci@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, <aliceryhl@google.com>,
 <bhelgaas@google.com>, <kwilczynski@kernel.org>, <ojeda@kernel.org>,
 <boqun@kernel.org>, <gary@garyguo.net>, <bjorn3_gh@protonmail.com>,
 <lossin@kernel.org>, <a.hindborg@kernel.org>, <tmgross@umich.edu>,
 <markus.probst@posteo.de>, <cjia@nvidia.com>, <smitra@nvidia.com>,
 <ankita@nvidia.com>, <aniketa@nvidia.com>, <kwankhede@nvidia.com>,
 <targupta@nvidia.com>, <kjaju@nvidia.com>, <alkumar@nvidia.com>,
 <acourbot@nvidia.com>, <jhubbard@nvidia.com>, <zhiwang@kernel.org>,
 <jgg@nvidia.com>, <alex@shazbot.org>, "Peter Colberg" <peter@colberg.org>
To: "Zhi Wang" <zhiw@nvidia.com>
From: "Danilo Krummrich" <dakr@kernel.org>
References: <cover.1790705494.git.zhiw@nvidia.com>
 <9b092d339961f744c7ded1e4f21911b66c80ecb4.1790759932.git.zhiw@nvidia.com>
In-Reply-To: <9b092d339961f744c7ded1e4f21911b66c80ecb4.1790759932.git.zhiw@nvidia.com>

On Wed Sep 30, 2026 at 12:18 PM CEST, Zhi Wang wrote:
> +pub struct SriovEnable<'callback> {

I understand why you chose 'callback, but I think just 'a is good enough.

> +    pdev: &'callback Device<device::CoreInternal<'callback>>,
> +    num_vfs: u32,

Please see patch 1.

> +}
> +
> +impl<'callback> SriovEnable<'callback> {
> +    /// Returns the number of VFs requested for this callback.
> +    pub fn num_vfs(&self) -> u32 {
> +        self.num_vfs
> +    }
> +
> +    /// Enables between one and the requested number of VFs.
> +    ///
> +    /// VF drivers can probe before this method returns, so the PF resou=
rces they access must
> +    /// already be initialized. The returned guard disables the VFs if s=
ubsequent setup fails.
> +    /// Return it from `sriov_enable()` to leave the VFs enabled on call=
back success.
> +    pub fn enable(self, num_vfs: u32) -> Result<SriovEnabled<'callback>>=
 {
> +        if num_vfs =3D=3D 0 || num_vfs > self.num_vfs {
> +            return Err(EINVAL);
> +        }
> +        let num_vfs =3D c_int::try_from(num_vfs).map_err(|_| EOVERFLOW)?=
;
> +
> +        // SAFETY: The PF's driver data and registration remain installe=
d throughout this callback.
> +        // The registration owns final VF teardown after the enable guar=
d is disarmed.
> +        if unsafe { (*self.pdev.as_raw()).vf_registration_data_rust }.is=
_null() {
> +            return Err(ENODEV);
> +        }
> +
> +        self.pdev.enable_sriov(num_vfs)?;
> +        Ok(SriovEnabled {
> +            pdev: Some(self.pdev),
> +            num_vfs,
> +        })
> +    }
> +}
> +
> +/// Enabled VFs awaiting successful completion of `sriov_enable()`.
> +pub struct SriovEnabled<'callback> {
> +    pdev: Option<&'callback Device<device::CoreInternal<'callback>>>,

This doesn't need to be an Option.

> +    num_vfs: c_int,
> +}
> +
> +impl SriovEnabled<'_> {
> +    #[expect(dead_code)]
> +    fn disarm(mut self) -> c_int {
> +        self.pdev =3D None;
> +        self.num_vfs

Instead of the Option dance, you can use ManuallyDrop to prevent the destru=
ctor
from running.

> +    }
> +}
> +
> +impl Drop for SriovEnabled<'_> {
> +    fn drop(&mut self) {
> +        if let Some(pdev) =3D self.pdev.take() {
> +            pdev.disable_sriov();
> +        }
> +    }
> +}