pci: Add support for reserving but not allocating slots

This can be used in a two pass approach where all configs that can hold
PCI devices are evaluated to reserve any specific PCI device IDs they
may need. Those device IDs will later be allocated when the devices are
added to the bus. The tri-state Free, Reserved, Allocated also catches
the problem of hotplugging a device with a specific, already used,
device ID.

Signed-off-by: Rob Bradford <rbradford@meta.com>

vmm/src/device_manager.rs

@@ -498,7 +498,7 @@ pub enum DeviceManagerError {
 
     /// Could not reserve the PCI device ID.
     #[error("Could not reserve the PCI device ID")]
-    GetPciDeviceId(#[source] pci::PciRootError),
+    ReservePciDeviceId(#[source] pci::PciRootError),
 
     /// Could not give the PCI device ID back.
     #[error("Could not give the PCI device ID back")]
@@ -4550,8 +4550,8 @@ impl DeviceManager {
                 .pci_bus
                 .lock()
                 .unwrap()
-                .get_device_id(pci_device_bdf.device() as usize)
-                .map_err(DeviceManagerError::GetPciDeviceId)?;
+                .allocate_device_id(Some(pci_device_bdf.device()))
+                .map_err(DeviceManagerError::AllocatePciDeviceId)?;
 
             (pci_segment_id, pci_device_bdf, resources)
         } else {