vmm: Add VFIO PCI device hotplug support

This commit finalizes the VFIO PCI hotplug support, based on all the
previous commits preparing for it.

One thing to notice, this does not support vIOMMU yet. This means we can
hotplug VFIO PCI devices, but we cannot attach them to an existing or a
new virtio-iommu device.

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

vmm/src/device_manager.rs

@@ -211,6 +211,9 @@ pub enum DeviceManagerError {
 
     /// Failed to spawn the block backend
     SpawnBlockBackend(io::Error),
+
+    /// Missing PCI bus.
+    NoPciBus,
 }
 pub type DeviceManagerResult<T> = result::Result<T, DeviceManagerError>;
 
@@ -447,6 +450,14 @@ pub struct DeviceManager {
     // Paravirtualized IOMMU
     #[cfg(feature = "pci_support")]
     iommu_device: Option<Arc<Mutex<vm_virtio::Iommu>>>,
+
+    // Bitmap of PCI devices to hotplug.
+    #[cfg(feature = "pci_support")]
+    pci_devices_up: u32,
+
+    // Bitmap of PCI devices to hotunplug.
+    #[cfg(feature = "pci_support")]
+    pci_devices_down: u32,
 }
 
 impl DeviceManager {
@@ -541,6 +552,10 @@ impl DeviceManager {
             kvm_device_fd: None,
             #[cfg(feature = "pci_support")]
             iommu_device: None,
+            #[cfg(feature = "pci_support")]
+            pci_devices_up: 0,
+            #[cfg(feature = "pci_support")]
+            pci_devices_down: 0,
         };
 
         device_manager
@@ -1632,7 +1647,39 @@ impl DeviceManager {
         return Ok(());
     }
 
-    pub fn add_device(&self, _path: String) -> DeviceManagerResult<()> {
+    #[cfg(feature = "pci_support")]
+    pub fn add_device(&mut self, path: String) -> DeviceManagerResult<()> {
+        let device_cfg = DeviceConfig {
+            path: PathBuf::from(path),
+            iommu: false,
+        };
+
+        let mut pci = if let Some(pci_bus) = &self.pci_bus {
+            pci_bus.lock().unwrap()
+        } else {
+            return Err(DeviceManagerError::NoPciBus);
+        };
+
+        let interrupt_manager = Arc::clone(&self.msi_interrupt_manager);
+
+        let device_fd = if let Some(device_fd) = &self.kvm_device_fd {
+            Arc::clone(&device_fd)
+        } else {
+            // If the VFIO KVM device file descriptor has not been created yet,
+            // it is created here and stored in the DeviceManager structure for
+            // future needs.
+            let device_fd = DeviceManager::create_kvm_device(&self.address_manager.vm_fd)?;
+            let device_fd = Arc::new(device_fd);
+            self.kvm_device_fd = Some(Arc::clone(&device_fd));
+            device_fd
+        };
+
+        let device_id =
+            self.add_vfio_device(&mut pci, &interrupt_manager, &device_fd, &device_cfg)?;
+
+        // Update the PCIU bitmap
+        self.pci_devices_up |= 1 << (device_id >> 3);
+
         Ok(())
     }
 }
@@ -1911,7 +1958,48 @@ impl Pausable for DeviceManager {
 impl Snapshotable for DeviceManager {}
 impl Migratable for DeviceManager {}
 
-impl BusDevice for DeviceManager {}
+#[cfg(feature = "pci_support")]
+const PCIU_FIELD_OFFSET: u64 = 0;
+#[cfg(feature = "pci_support")]
+const PCID_FIELD_OFFSET: u64 = 4;
+
+#[cfg(feature = "pci_support")]
+const PCIU_FIELD_SIZE: usize = 4;
+#[cfg(feature = "pci_support")]
+const PCID_FIELD_SIZE: usize = 4;
+
+impl BusDevice for DeviceManager {
+    fn read(&mut self, base: u64, offset: u64, data: &mut [u8]) {
+        #[cfg(feature = "pci_support")]
+        match offset {
+            PCIU_FIELD_OFFSET => {
+                assert!(data.len() == PCIU_FIELD_SIZE);
+                data.copy_from_slice(&self.pci_devices_up.to_le_bytes());
+                // Clear the PCIU bitmap
+                self.pci_devices_up = 0;
+            }
+            PCID_FIELD_OFFSET => {
+                assert!(data.len() == PCID_FIELD_SIZE);
+                data.copy_from_slice(&self.pci_devices_down.to_le_bytes());
+                // Clear the PCID bitmap
+                self.pci_devices_down = 0;
+            }
+            _ => {}
+        }
+
+        debug!(
+            "PCI_HP_REG_R: base 0x{:x}, offset 0x{:x}, data {:?}",
+            base, offset, data
+        )
+    }
+
+    fn write(&mut self, base: u64, offset: u64, data: &[u8]) {
+        debug!(
+            "PCI_HP_REG_W: base 0x{:x}, offset 0x{:x}, data {:?}",
+            base, offset, data
+        )
+    }
+}
 
 impl Drop for DeviceManager {
     fn drop(&mut self) {

vmm/src/vm.rs

@@ -164,6 +164,9 @@ pub enum Error {
 
     /// Memory manager error
     MemoryManager(MemoryManagerError),
+
+    /// No PCI support
+    NoPciSupport,
 }
 pub type Result<T> = result::Result<T, Error>;
 
@@ -540,11 +543,14 @@ impl Vm {
         Ok(())
     }
 
-    pub fn add_device(&mut self, path: String) -> Result<()> {
+    pub fn add_device(&mut self, _path: String) -> Result<()> {
+        if cfg!(feature = "pci_support") {
+            #[cfg(feature = "pci_support")]
+            {
                 self.devices
                     .lock()
                     .unwrap()
-            .add_device(path)
+                    .add_device(_path)
                     .map_err(Error::DeviceManager)?;
 
                 self.devices
@@ -552,8 +558,12 @@ impl Vm {
                     .unwrap()
                     .notify_hotplug(HotPlugNotificationFlags::PCI_DEVICES_CHANGED)
                     .map_err(Error::DeviceManager)?;
+            }
 
             Ok(())
+        } else {
+            Err(Error::NoPciSupport)
+        }
     }
 
     fn os_signal_handler(signals: Signals, console_input_clone: Arc<Console>, on_tty: bool) {