From 900237a541a680e9097559eb67e329bfb0960d75 Mon Sep 17 00:00:00 2001
From: Daniel Verkamp <dverkamp@chromium.org>
Date: Thu, 26 May 2022 13:29:27 -0700
Subject: [PATCH] devices: virtio-iommu: do not hold RefCell or lock across
 async

Retrieve the translation response, which involves taking a mutable
borrow of a RefCell as well as locking a Mutex, inside its own block so
that the references are dropped before using await again.

Fixes two new clippy warnings from Rust 1.61.0:
- <https://rust-lang.github.io/rust-clippy/master/index.html#await_holding_refcell_ref>
- <https://rust-lang.github.io/rust-clippy/master/index.html#await_holding_lock>

BUG=None
TEST=tools/clippy # Rust 1.61.0

Change-Id: If573af56968dceeae72a61a74f9f69dad8730364
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3671596
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Anton Romanov <romanton@google.com>
Commit-Queue: Daniel Verkamp <dverkamp@chromium.org>
---
 devices/src/virtio/iommu.rs | 40 +++++++++++++++++++------------------
 1 file changed, 21 insertions(+), 19 deletions(-)

diff --git a/devices/src/virtio/iommu.rs b/devices/src/virtio/iommu.rs
index 42eae4657c..17d9fe8560 100644
--- a/devices/src/virtio/iommu.rs
+++ b/devices/src/virtio/iommu.rs
@@ -702,25 +702,27 @@ async fn handle_translate_request(
             iova,
             size,
         } = request_tube.next().await.map_err(IommuError::Tube)?;
-        if let Some(mapper) = endpoints.borrow_mut().get(&endpoint_id) {
-            response_tubes
-                .get(&endpoint_id)
-                .unwrap()
-                .send(
-                    mapper
-                        .lock()
-                        .translate(iova, size)
-                        .map_err(|e| {
-                            error!("Failed to handle TranslateRequest: {}", e);
-                            e
-                        })
-                        .ok(),
-                )
-                .await
-                .map_err(IommuError::Tube)?;
-        } else {
-            error!("endpoint_id {} not found", endpoint_id)
-        }
+        let translate_response: Option<Vec<MemRegion>> =
+            if let Some(mapper) = endpoints.borrow_mut().get(&endpoint_id) {
+                mapper
+                    .lock()
+                    .translate(iova, size)
+                    .map_err(|e| {
+                        error!("Failed to handle TranslateRequest: {}", e);
+                        e
+                    })
+                    .ok()
+            } else {
+                error!("endpoint_id {} not found", endpoint_id);
+                continue;
+            };
+
+        response_tubes
+            .get(&endpoint_id)
+            .unwrap()
+            .send(translate_response)
+            .await
+            .map_err(IommuError::Tube)?;
     }
 }