Function validate_pci_group_for_passthrough

crates/openshell-vfio/src/pci.rs:370–421

Dry-run validation that [`prepare_pci_group_for_passthrough`] would accept this slice of BDFs as a complete IOMMU group right now. Mirrors the structural checks of the prepare call without performing any kernel-state-mutating operations. Intended for `ValidateSandboxCreate`-style pre-flight paths. Rejects: - empty slices (`EmptyGroup`), - malformed BDFs (`InvalidBdf`), - duplicate entries (`Inva

(
    sysfs: &SysfsRoot,
    bdfs: &[&str],
)

/// Unlike [`validate_pci_for_passthrough`], this function does not consult
/// the current binding state of any device; it is purely structural.
pub fn validate_pci_group_for_passthrough(
    sysfs: &SysfsRoot,
    bdfs: &[&str],
) -> Result<(), VfioError> {
    let (primary, companions) = bdfs.split_first().ok_or(VfioError::EmptyGroup)?;

    for bdf in bdfs {
        validate_bdf(bdf)?;
        if !sysfs.pci_device_ref(bdf).exists() {
            return Err(VfioError::DeviceNotFound {
                bdf: (*bdf).to_string(),
            });
        }
    }

    let declared: BTreeSet<&str> = bdfs.iter().copied().collect();
    if declared.len() != bdfs.len() {
        // Duplicate entries would make the IOMMU equality check pass while
        // double-binding the same device.
        return Err(VfioError::InvalidBdf {
            bdf: format!("duplicate entries in PCI group: {bdfs:?}"),
        });
    }

    let expected_group = sysfs.pci_device_ref(primary).iommu_group()?;
    for bdf in companions {
        let g = sysfs.pci_device_ref(bdf).iommu_group()?;
        if g != expected_group {
            return Err(VfioError::GroupMismatch {
                bdf: (*bdf).to_string(),
                expected_group,
                actual_group: g,
            });
        }
    }

    let kernel_peers = sysfs.iommu_group_devices(expected_group)?;
    let undeclared: Vec<String> = kernel_peers
        .iter()
        .filter(|p| !declared.contains(p.as_str()))
        .cloned()
        .collect();
    if !undeclared.is_empty() {
        return Err(VfioError::IommuGroupConflict {
            bdf: (*primary).to_string(),
            group: expected_group,
            peers: undeclared,
        });
    }

    Ok(())
}

/// Atomically bind every `PCIe` device in a shared IOMMU group to `vfio-pci`.
///