device_manager: AArch64: add a field to set/get GIC device entity

In AArch64 systems, the state of GIC device can only be
retrieved from `KVM_GET_DEVICE_ATTR` ioctl. Therefore to implement
saving/restoring the GIC states, we need to make sure that the
GIC object (either the file descriptor or the device itself) can
be extracted after the VM is started.

This commit refactors the code of GIC creation by adding a new
field `gic_device_entity` in device manager and methods to set/get
this field. The GIC object can be therefore saved in the device
manager after calling `arch::configure_system`.

Signed-off-by: Henry Wang <Henry.Wang@arm.com>

arch/src/aarch64/gic/mod.rs

@@ -26,7 +26,7 @@ pub enum Error {
 }
 type Result<T> = result::Result<T, Error>;
 
-pub trait GICDevice {
+pub trait GICDevice: Send {
     /// Returns the hypervisor agnostic Device of the GIC device
     fn device(&self) -> &Arc<dyn hypervisor::Device>;
 

arch/src/aarch64/mod.rs

@@ -14,6 +14,7 @@ pub mod regs;
 pub use self::fdt::DeviceInfoForFDT;
 use crate::DeviceType;
 use crate::RegionType;
+use aarch64::gic::GICDevice;
 use hypervisor::kvm::kvm_bindings;
 use std::collections::HashMap;
 use std::ffi::CStr;
@@ -146,7 +147,7 @@ pub fn configure_system<T: DeviceInfoForFDT + Clone + Debug, S: ::std::hash::Bui
     device_info: &HashMap<(DeviceType, String), T, S>,
     initrd: &Option<super::InitramfsConfig>,
     pci_space_address: &Option<(u64, u64)>,
-) -> super::Result<()> {
+) -> super::Result<Box<dyn GICDevice>> {
     // If pci_space_address is present, it means PCI devices are used ("pci" feature enabled).
     // Then GITv3-ITS is required for MSI messaging.
     // Otherwise ("mmio" feature enabled), any version of GIC is OK.
@@ -164,7 +165,7 @@ pub fn configure_system<T: DeviceInfoForFDT + Clone + Debug, S: ::std::hash::Bui
     )
     .map_err(Error::SetupFDT)?;
 
-    Ok(())
+    Ok(gic_device)
 }
 
 /// Returns the memory address where the initramfs could be loaded.