feature(hypervisor-dmesg): xencall: add read_console_ring_raw hypercall wrapper

crates/xen/xencall/examples/console_read.rs

@@ -0,0 +1,18 @@
+use xencall::error::Result;
+use xencall::XenCall;
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    env_logger::init();
+
+    let call = XenCall::open(0)?;
+    let index = 0 as u32;
+    let (buf, newindex) = call.read_console_ring_raw(false, index).await?;
+
+    match std::str::from_utf8(&buf[..newindex as usize]) {
+        Ok(v) => print!("{}", v),
+        _ => panic!("unable to decode Xen console messages"),
+    };
+
+    Ok(())
+}