vmm: Add iommu=on|off option for --vsock

Having the virtual IOMMU created with --iommu is one thing, but we also
need a way to decide if a virtio-vsock device should be attached to this
virtual IOMMU or not. That's why we introduce an extra option "iommu"
with the value "on" or "off". By default, the device is not attached,
which means "iommu=off".

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

src/main.rs

@@ -219,7 +219,7 @@ fn main() {
                 .long("vsock")
                 .help(
                     "Virtio VSOCK parameters \"cid=<context_id>,\
-                     sock=<socket_path>\"",
+                     sock=<socket_path>,iommu=on|off\"",
                 )
                 .takes_value(true)
                 .min_values(1)