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.

Set the flag managed_sriov to always disable SR-IOV when a Rust PCI
driver is unbound from a PF device. This ensures that when a Virtual
Function (VF) is bound to a driver, the corresponding Physical Function
(PF) is bound to a driver, too, which is a prerequisite for exposing a
safe Rust API that allows a VF driver to obtain the PF device for a VF
device and subsequently access the private data of the PF driver.

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Peter Colberg <pcolberg@redhat.com>
---
Changes in v2:
- Set flag managed_sriov to disable SR-IOV on remove().
- Use to_result() to handle error in enable_sriov().
- Note Bound device context in SAFETY comments.
---
 rust/kernel/pci.rs | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index af74ddff6114db3c2ce8e228c5a953cd0769e8a5..e1cab1574a3d309d25bf5267c0b0d8da8fb66d44 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -82,6 +82,7 @@ unsafe fn register(
             (*pdrv.get()).probe = Some(Self::probe_callback);
             (*pdrv.get()).remove = Some(Self::remove_callback);
             (*pdrv.get()).id_table = T::ID_TABLE.as_ptr();
+            (*pdrv.get()).managed_sriov = true;
         }
 
         // SAFETY: `pdrv` is guaranteed to be a valid `DriverType`.
@@ -458,6 +459,38 @@ 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.
+        //
+        // The Core device context inherits from the Bound device context,
+        // which guarantees that the PF device is bound to a driver.
+        to_result(unsafe { bindings::pci_enable_sriov(self.as_raw(), nr_virtfn) })
+    }
+
+    /// 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.
+        //
+        // The Core device context inherits from the Bound device context,
+        // which guarantees that the PF device is bound to a driver.
+        unsafe { bindings::pci_disable_sriov(self.as_raw()) };
+    }
 }
 
 // SAFETY: `pci::Device` is a transparent wrapper of `struct pci_dev`.

-- 
2.52.0