linux-kernel - Re: [PATCH v2 0/4] Improve soundness of bus device abstractions

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Message-ID: <Z9gLeaQqZOef0Fqz@pollux>
Date: Mon, 17 Mar 2025 12:46:01 +0100
From: Danilo Krummrich <dakr@...nel.org>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: rafael@...nel.org, bhelgaas@...gle.com, ojeda@...nel.org,
	alex.gaynor@...il.com, boqun.feng@...il.com, gary@...yguo.net,
	bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
	a.hindborg@...nel.org, aliceryhl@...gle.com, tmgross@...ch.edu,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2 0/4] Improve soundness of bus device abstractions

On Sat, Mar 15, 2025 at 09:34:17AM +0100, Greg KH wrote:
> On Fri, Mar 14, 2025 at 05:09:03PM +0100, Danilo Krummrich wrote:
> > Currently, when sharing references of bus devices (e.g. ARef<pci::Device>), we
> > do not have a way to restrict which functions of a bus device can be called.
> > 
> > Consequently, it is possible to call all bus device functions concurrently from
> > any context. This includes functions, which access fields of the (bus) device,
> > which are not protected against concurrent access.
> > 
> > This is improved by applying an execution context to the bus device in form of a
> > generic type.
> > 
> > For instance, the PCI device reference that is passed to probe() has the type
> > pci::Device<Core>, which implements all functions that are only allowed to be
> > called from bus callbacks.
> > 
> > The implementation for the default context (pci::Device) contains all functions
> > that are safe to call from any context concurrently.
> > 
> > The context types can be extended as required, e.g. to limit availability  of
> > certain (bus) device functions to probe().
> > 
> > A branch containing the patches can be found in [1].
> > 
> > [1] https://web.git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/device
> > 
> > Changes in v2:
> >   - make `DeviceContext` trait sealed
> >   - impl From<&pci::Device<device::Core>> for ARef<pci::Device>
> >   - impl From<&platform::Device<device::Core>> for ARef<platform::Device>
> >   - rebase onto v6.14-rc6
> >   - apply RBs
> > 
> > Danilo Krummrich (4):
> >   rust: pci: use to_result() in enable_device_mem()
> >   rust: device: implement device context marker
> >   rust: pci: fix unrestricted &mut pci::Device
> >   rust: platform: fix unrestricted &mut platform::Device
> > 
> >  rust/kernel/device.rs                |  26 +++++
> >  rust/kernel/pci.rs                   | 137 +++++++++++++++++----------
> >  rust/kernel/platform.rs              |  95 +++++++++++++------
> >  samples/rust/rust_driver_pci.rs      |   8 +-
> >  samples/rust/rust_driver_platform.rs |  11 ++-
> >  5 files changed, 187 insertions(+), 90 deletions(-)
> 
> Thanks for doing this work, looks good to me.  Mind if I suck it into
> the driver-core tree now?  Or do you want it to go through a different
> tree?

This series has a conflict with nova-core, it will require the following fixup
in -next and Linus' tree when he pulls things.

diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
index 63c19f140fbd..a08fb6599267 100644
--- a/drivers/gpu/nova-core/driver.rs
+++ b/drivers/gpu/nova-core/driver.rs
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 
-use kernel::{bindings, c_str, pci, prelude::*};
+use kernel::{bindings, c_str, device::Core, pci, prelude::*};
 
 use crate::gpu::Gpu;
 
@@ -27,7 +27,7 @@ impl pci::Driver for NovaCore {
     type IdInfo = ();
     const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
 
-    fn probe(pdev: &mut pci::Device, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
+    fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
         dev_dbg!(pdev.as_ref(), "Probe Nova Core GPU driver.\n");
 
         pdev.enable_device_mem()?;