Only clear io buffer after unsuccesfull guest call.

Signed-off-by: Ludvig Liljenberg <[email protected]>

Undo stuff that breaks unwinding

Signed-off-by: Ludvig Liljenberg <[email protected]>

Author: ludfjig

src/hyperlight_host/src/sandbox/initialized_multi_use.rs

@@ -423,9 +423,14 @@ impl MultiUseSandbox {
                 .get_guest_function_call_result()
         })();
 
-        // TODO: Do we want to allow re-entrant guest function calls?
-        self.get_mgr_wrapper_mut().as_mut().clear_io_buffers();
-
+        // In the happy path we do not need to clear io-buffers from the host because:
+        // - the serialized guest function call is zeroed out by the guest during deserialization, see call to `try_pop_shared_input_data_into::<FunctionCall>()`
+        // - the serialized guest function result is zeroed out by us (the host) during deserialization, see `get_guest_function_call_result`
+        // - any serialized host function call are zeroed out by us (the host) during deserialization, see `get_host_function_call`
+        // - any serialized host function result is zeroed out by the guest during deserialization, see `get_host_return_value`
+        if res.is_err() {
+            self.get_mgr_wrapper_mut().as_mut().clear_io_buffers();
+        }
         res
     }