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

Having the virtual IOMMU created with --iommu is one thing, but we also
need a way to decide if a virtio-console 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

@@ -187,7 +187,10 @@ fn main() {
         .arg(
             Arg::with_name("console")
                 .long("console")
-                .help("Control (virtio) console: off|null|tty|file=/path/to/a/file")
+                .help(
+                    "Control (virtio) console: \"off|null|tty|file=/path/to/a/file,\
+                     iommu=on|off\"",
+                )
                 .default_value("tty")
                 .group("vm-config"),
         )