vmm: Share the guest memory instead of cloning it

The VMM guest memory was cloned (copied) everywhere the code needed to
have ownership of it. In order to clean the code, and in anticipation
for future support of modifying this guest memory instance at runtime,
it is important that every part of the code share the same instance.

Because VirtioDevice implementations need to have access to it from
different threads, that's why Arc must be used in this case.

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

vfio/src/vfio_device.rs

@@ -513,14 +513,18 @@ pub struct VfioDevice {
     group: VfioGroup,
     regions: Vec<VfioRegion>,
     irqs: HashMap<u32, VfioIrq>,
-    mem: GuestMemoryMmap,
+    mem: Arc<GuestMemoryMmap>,
 }
 
 impl VfioDevice {
     /// Create a new vfio device, then guest read/write on this device could be
     /// transfered into kernel vfio.
     /// sysfspath specify the vfio device path in sys file system.
-    pub fn new(sysfspath: &Path, device_fd: Arc<DeviceFd>, mem: GuestMemoryMmap) -> Result<Self> {
+    pub fn new(
+        sysfspath: &Path,
+        device_fd: Arc<DeviceFd>,
+        mem: Arc<GuestMemoryMmap>,
+    ) -> Result<Self> {
         let uuid_path: PathBuf = [sysfspath, Path::new("iommu_group")].iter().collect();
         let group_path = uuid_path.read_link().map_err(|_| VfioError::InvalidPath)?;
         let group_osstr = group_path.file_name().ok_or(VfioError::InvalidPath)?;