vmm: Use new Resource type PciBar

Instead of defining some very generic resources as PioAddressRange or
MmioAddressRange for each PCI BAR, let's move to the new Resource type
PciBar in order to make things clearer. This allows the code for being
more readable, but also removes the need for hard assumptions about the
MMIO and PIO ranges. PioAddressRange and MmioAddressRange types can be
used to describe everything except PCI BARs. BARs are very special as
they can be relocated and have special information we want to carry
along with them.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

virtio-devices/src/transport/pci_device.rs

@@ -846,17 +846,22 @@ impl PciDevice for VirtioPciDevice {
         let mut bars = Vec::new();
         let device_clone = self.device.clone();
         let device = device_clone.lock().unwrap();
-        let settings_bar_addr = if let Some(resources) = &resources {
-            if resources.is_empty() {
+
+        let mut settings_bar_addr = None;
+        if let Some(resources) = &resources {
+            for resource in resources {
+                if let Resource::PciBar { index, base, .. } = resource {
+                    if *index == VIRTIO_COMMON_BAR_INDEX {
+                        settings_bar_addr = Some(GuestAddress(*base));
+                        break;
+                    }
+                }
+            }
+            // Error out if no resource was matching the BAR id.
+            if settings_bar_addr.is_none() {
                 return Err(PciDeviceError::MissingResource);
             }
-            match resources[VIRTIO_COMMON_BAR_INDEX] {
-                Resource::MmioAddressRange { base, .. } => Some(GuestAddress(base)),
-                _ => return Err(PciDeviceError::InvalidResourceType),
-            }
-        } else {
-            None
-        };
+        }
 
         // Allocate the virtio-pci capability BAR.
         // See http://docs.oasis-open.org/virtio/virtio/v1.0/cs04/virtio-v1.0-cs04.html#x1-740004