pci: add unit tests to PciSegment

Add some unit tests to PciSegment. We now test that the
next_device_bdf() method and the initialization logic work as expected.
We also check that the configuration space of the PCI segment is
correctly registered with the MMIO and, on x86, PIO bus.

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Author: Babis Chalios

src/vmm/src/devices/pci/pci_segment.rs

@@ -462,3 +462,99 @@ impl Aml for PciSegment {
         .append_aml_bytes(v)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{arch, utils::u64_to_usize};
+
+    use super::*;
+
+    #[test]
+    fn test_pci_segment_build() {
+        let resource_allocator = Arc::new(ResourceAllocator::new().unwrap());
+        let pci_irq_slots = &[0u8; 32];
+        let pci_segment = PciSegment::new(0, &resource_allocator, pci_irq_slots).unwrap();
+
+        assert_eq!(pci_segment.id, 0);
+        assert_eq!(
+            pci_segment.start_of_mem32_area,
+            arch::MEM_32BIT_DEVICES_START
+        );
+        assert_eq!(
+            pci_segment.end_of_mem32_area,
+            arch::MEM_32BIT_DEVICES_START + arch::MEM_32BIT_DEVICES_SIZE - 1
+        );
+        assert_eq!(
+            pci_segment.start_of_mem64_area,
+            arch::MEM_64BIT_DEVICES_START
+        );
+        assert_eq!(
+            pci_segment.end_of_mem64_area,
+            arch::MEM_64BIT_DEVICES_START + arch::MEM_64BIT_DEVICES_SIZE - 1
+        );
+        assert_eq!(pci_segment.mmio_config_address, arch::PCI_MMCONFIG_START);
+        assert_eq!(pci_segment.proximity_domain, 0);
+        assert_eq!(pci_segment.pci_devices_up, 0);
+        assert_eq!(pci_segment.pci_devices_down, 0);
+        assert_eq!(pci_segment.pci_irq_slots, [0u8; 32]);
+    }
+
+    #[cfg(target_arch = "x86_64")]
+    #[test]
+    fn test_io_bus() {
+        let resource_allocator = Arc::new(ResourceAllocator::new().unwrap());
+        let pci_irq_slots = &[0u8; 32];
+        let pci_segment = PciSegment::new(0, &resource_allocator, pci_irq_slots).unwrap();
+
+        let mut data = [0u8; u64_to_usize(PCI_CONFIG_IO_PORT_SIZE)];
+        resource_allocator
+            .pio_bus
+            .read(PCI_CONFIG_IO_PORT, &mut data)
+            .unwrap();
+
+        resource_allocator
+            .pio_bus
+            .read(PCI_CONFIG_IO_PORT + PCI_CONFIG_IO_PORT_SIZE, &mut data)
+            .unwrap_err();
+    }
+
+    #[test]
+    fn test_mmio_bus() {
+        let resource_allocator = Arc::new(ResourceAllocator::new().unwrap());
+        let pci_irq_slots = &[0u8; 32];
+        let pci_segment = PciSegment::new(0, &resource_allocator, pci_irq_slots).unwrap();
+
+        let mut data = [0u8; u64_to_usize(PCI_MMIO_CONFIG_SIZE_PER_SEGMENT)];
+
+        resource_allocator
+            .mmio_bus
+            .read(pci_segment.mmio_config_address, &mut data)
+            .unwrap();
+        resource_allocator
+            .mmio_bus
+            .read(
+                pci_segment.mmio_config_address + PCI_MMIO_CONFIG_SIZE_PER_SEGMENT,
+                &mut data,
+            )
+            .unwrap_err();
+    }
+
+    #[test]
+    fn test_next_device_bdf() {
+        let resource_allocator = Arc::new(ResourceAllocator::new().unwrap());
+        let pci_irq_slots = &[0u8; 32];
+        let pci_segment = PciSegment::new(0, &resource_allocator, pci_irq_slots).unwrap();
+
+        // Start checking from device id 1, since 0 is allocated to the Root port.
+        for dev_id in 1..32 {
+            let bdf = pci_segment.next_device_bdf().unwrap();
+            // In our case we have a single Segment with id 0, which has
+            // a single bus with id 0. Also, each device of ours has a
+            // single function.
+            assert_eq!(bdf, PciBdf::new(0, 0, dev_id, 0));
+        }
+
+        // We can only have 32 devices on a segment
+        pci_segment.next_device_bdf().unwrap_err();
+    }
+}