kratart: support for krata channels for two-way byte communication

crates/xen/xengnt/src/error.rs

@@ -8,8 +8,8 @@ pub enum Error {
     Io(#[from] io::Error),
     #[error("failed to read structure")]
     StructureReadFailed,
-    #[error("mmap failed")]
-    MmapFailed,
+    #[error("mmap failed: {0}")]
+    MmapFailed(nix::errno::Errno),
 }
 
 pub type Result<T> = std::result::Result<T, Error>;