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

Danilo Krummrich
2025-03-17T11:46:07Z

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()?;