[PATCH v3 00/10] rust: pci: add abstractions for SR-IOV capability

[Peter Colberg <pcolberg@redhat.com>]

Add Rust abstractions for the Single Root I/O Virtualization (SR-IOV)
capability of a PCI device. Provide a minimal set of wrappers for the
SR-IOV C API to enable and disable SR-IOV for a device, and query if
a PCI device is a Physical Function (PF) or Virtual Function (VF).

Using the #[vtable] attribute, extend the pci::Driver trait with an
optional bus callback sriov_configure() that is invoked when a
user-space application writes the number of VFs to the sysfs file
`sriov_numvfs` to enable SR-IOV, or zero to disable SR-IOV [1].

Add a method physfn() to return the Physical Function (PF) device for a
Virtual Function (VF) device in the bound device context. Unlike for a
PCI driver written in C, guarantee that when a VF device is bound to a
driver, the underlying PF device is bound to a driver, too.

When a device with enabled VFs is unbound from a driver, invoke the
sriov_configure() callback to disable SR-IOV before the remove()
callback. To ensure the guarantee is upheld, call disable_sriov()
to remove all VF devices if the driver has not done so already.

For PF drivers written in C, disabling SR-IOV on remove() may be opted
into by setting the flag managed_sriov in the pci_driver structure. For
PF drivers written in Rust, disabling SR-IOV on unbind() is mandatory.

This series is based on Danilo Krummrich's series "Device::drvdata() and
driver/driver interaction (auxiliary)" applied to driver-core-next,
which similarly guarantees that when an auxiliary bus device is bound to
a driver, the underlying parent device is bound to a driver, too [2, 3].

Add an SR-IOV driver sample that exercises the SR-IOV capability using
QEMU's 82576 (igb) emulation and was used to test the abstractions [4].

[1] https://docs.kernel.org/PCI/pci-iov-howto.html
[2] https://lore.kernel.org/rust-for-linux/20251020223516.241050-1-dakr@kernel.org/
[3] https://lore.kernel.org/rust-for-linux/20260107103511.570525-7-dakr@kernel.org/
[4] https://www.qemu.org/docs/master/system/devices/igb.html

Signed-off-by: Peter Colberg <pcolberg@redhat.com>
---
Changes in v3:
- Replace SR_IOV -> SR-IOV in description.
- Drop redundant `.as_ref()` for `dev_*` prints.
- Link to v2: https://lore.kernel.org/r/20260205-rust-pci-sriov-v2-0-ef9400c7767b@redhat.com

Changes in v2:
- Move logic to disable SR-IOV on remove() from Rust to C.
- Add driver flag managed_sriov to opt into disabling SR-IOV on remove().
- Demonstrate flag managed_sriov for dfl-pci driver.
- Uphold safety guarantee for physfn() when PF driver is written in C.
- Let physfn() return error if driver flag managed_sriov is unset.
- Use "kernel vertical" style on imports.
- Use to_result() to handle error in enable_sriov().
- Note Bound device context in SAFETY comments for {enable,disable}_sriov().
- Demonstrate how to reach driver data of PF device from VF device.
- Add missing #[vtable] attribute in PCI driver trait example.
- Add missing #[vtable] attribute in nova-core driver.
- Define struct MyDriver such that physfn() example compiles.
- Replace VF -> PF in doc comment of is_physfn().
- Add #[inline] to is_physfn() and is_virtfn().
- Link to v1: https://lore.kernel.org/r/20251119-rust-pci-sriov-v1-0-883a94599a97@redhat.com

---
John Hubbard (1):
      rust: pci: add is_virtfn(), to check for VFs

Peter Colberg (9):
      PCI: add driver flag to opt into disabling SR-IOV on remove()
      fpga: dfl-pci: set driver flag to disable SR-IOV on remove()
      rust: pci: add {enable,disable}_sriov(), to control SR-IOV capability
      rust: pci: add vtable attribute to pci::Driver trait
      rust: pci: add bus callback sriov_configure(), to control SR-IOV from sysfs
      rust: pci: add is_physfn(), to check for PFs
      rust: pci: add num_vf(), to return number of VFs
      rust: pci: add physfn(), to return PF device for VF device
      samples: rust: add SR-IOV driver sample

 MAINTAINERS                           |   1 +
 drivers/fpga/dfl-pci.c                |  17 ++--
 drivers/gpu/nova-core/driver.rs       |   1 +
 drivers/pci/iov.c                     |  41 ++++++++-
 drivers/pci/pci-driver.c              |   3 +-
 drivers/pci/pci.h                     |   2 +
 include/linux/pci.h                   |   8 ++
 rust/kernel/pci.rs                    | 165 ++++++++++++++++++++++++++++++++++
 samples/rust/Kconfig                  |  11 +++
 samples/rust/Makefile                 |   1 +
 samples/rust/rust_dma.rs              |   1 +
 samples/rust/rust_driver_auxiliary.rs |   1 +
 samples/rust/rust_driver_pci.rs       |   1 +
 samples/rust/rust_driver_sriov.rs     | 127 ++++++++++++++++++++++++++
 14 files changed, 366 insertions(+), 14 deletions(-)
---
base-commit: 1b9a5bc8513d081c1bfe2c096b6dc502a4660f47
change-id: 20251026-rust-pci-sriov-ca8f501b2ae3

Best regards,
-- 
Peter Colberg <pcolberg@redhat.com>