vmm: Provide DMA mapping handlers to virtio-mem devices

Now that virtio-mem devices can update VFIO mappings through dedicated
handlers, let's provide them from the DeviceManager.

Important to note these handlers should either be provided to virtio-mem
devices or to the unique virtio-iommu device. This must be mutually
exclusive.

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

pci/src/vfio.rs

@@ -354,6 +354,10 @@ impl VfioPciDevice {
         Ok(vfio_pci_device)
     }
 
+    pub fn iommu_attached(&self) -> bool {
+        self.iommu_attached
+    }
+
     fn enable_intx(&mut self) -> Result<()> {
         if let Some(intx) = &mut self.interrupt.intx {
             if !intx.enabled {