pci: add support for snapshotting PCI devices

At the moment, the logic just restores the device manager and add the
PCIe root complex if PCI is enabled.

Signed-off-by: Babis Chalios <[email protected]>

Author: bchalios

src/vmm/src/device_manager/mod.rs

@@ -265,6 +265,8 @@ pub struct DevicesState {
     pub mmio_state: persist::DeviceStates,
     /// ACPI devices state
     pub acpi_state: persist::ACPIDeviceManagerState,
+    /// PCI devices state
+    pub pci_state: pci_mngr::PciDevicesState,
 }
 
 #[derive(Debug, thiserror::Error, displaydoc::Display)]
@@ -273,6 +275,8 @@ pub enum DevicePersistError {
     MmioRestore(#[from] persist::DevicePersistError),
     /// Error restoring ACPI devices: {0}
     AcpiRestore(#[from] persist::ACPIDeviceManagerRestoreError),
+    /// Error restoring PCI devices: {0}
+    PciRestore(#[from] PciManagerError),
     /// Error notifying VMGenID device: {0}
     VmGenidUpdate(#[from] std::io::Error),
     /// Error resetting serial console: {0}
@@ -295,6 +299,7 @@ impl DeviceManager {
         DevicesState {
             mmio_state: self.mmio_devices.save(),
             acpi_state: self.acpi_devices.save(),
+            pci_state: self.pci_devices.save(),
         }
     }
 
@@ -366,6 +371,10 @@ impl DeviceManager {
         self.acpi_devices = ACPIDeviceManager::restore(acpi_ctor_args, &state.acpi_state)?;
         self.acpi_devices.notify_vmgenid()?;
 
+        // Restore PCI devices
+        self.pci_devices
+            .restore(&state.pci_state, &self.resource_allocator)?;
+
         Ok(())
     }
 }

src/vmm/src/device_manager/pci_mngr.rs

@@ -3,6 +3,7 @@
 
 use std::sync::Arc;
 
+use serde::{Deserialize, Serialize};
 use vm_device::BusError;
 
 use super::resources::ResourceAllocator;
@@ -42,4 +43,27 @@ impl PciDevices {
 
         Ok(())
     }
+
+    pub fn save(&self) -> PciDevicesState {
+        PciDevicesState {
+            pci_enabled: self.pci_segment.is_some(),
+        }
+    }
+
+    pub fn restore(
+        &mut self,
+        state: &PciDevicesState,
+        resource_allocator: &Arc<ResourceAllocator>,
+    ) -> Result<(), PciManagerError> {
+        if state.pci_enabled {
+            self.attach_pci_segment(resource_allocator)?;
+        }
+
+        Ok(())
+    }
+}
+
+#[derive(Default, Debug, Clone, Serialize, Deserialize)]
+pub struct PciDevicesState {
+    pci_enabled: bool,
 }