From 8509e2229c3e954383e031c7e519bf8e769043e6 Mon Sep 17 00:00:00 2001
From: Keiichi Watanabe <keiichiw@chromium.org>
Date: Wed, 9 Jun 2021 22:50:55 +0900
Subject: [PATCH] vhost_user_devices: Remove O_NONBLOCK from given kick FD

Remove O_NONBLOCK from kick FD as uring_executor assumes so. Otherwise,
we may get EAGAIN when we read a value.

This patch is needed to use QEMU as a vmm.

BUG=b:190450677
TEST=run QEMU and vhost-user-net-devices with uring_executor

Change-Id: I8dc533c824909eb0298e4264f45d7a62998ebc6a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2950028
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
---
 Cargo.lock                    | 1 +
 vhost_user_devices/Cargo.toml | 1 +
 vhost_user_devices/src/lib.rs | 9 +++++++++
 3 files changed, 11 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index b2b8be9301..69027f0399 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1171,6 +1171,7 @@ dependencies = [
  "once_cell",
  "remain",
  "sync",
+ "sys_util",
  "tempfile",
  "thiserror",
  "virtio_sys",
diff --git a/vhost_user_devices/Cargo.toml b/vhost_user_devices/Cargo.toml
index 71d5596c22..0aae93cec5 100644
--- a/vhost_user_devices/Cargo.toml
+++ b/vhost_user_devices/Cargo.toml
@@ -32,6 +32,7 @@ net_util = { path = "../net_util", optional = true }
 once_cell = "1.7.2"
 remain = "*"
 sync = { path = "../sync" }
+sys_util = { path = "../sys_util" }
 thiserror = "*"
 virtio_sys = { path = "../virtio_sys", optional = true }
 vm_memory = { path = "../vm_memory" }
diff --git a/vhost_user_devices/src/lib.rs b/vhost_user_devices/src/lib.rs
index 40985a8587..13a4a8714b 100644
--- a/vhost_user_devices/src/lib.rs
+++ b/vhost_user_devices/src/lib.rs
@@ -56,6 +56,7 @@ use cros_async::{AsyncError, AsyncWrapper, Executor};
 use devices::virtio::{Queue, SignalableInterrupt};
 use remain::sorted;
 use sync::Mutex;
+use sys_util::clear_fd_flags;
 use thiserror::Error as ThisError;
 use vm_memory::{GuestAddress, GuestMemory, MemoryRegion};
 use vmm_vhost::vhost_user::message::{
@@ -475,6 +476,14 @@ impl<B: VhostUserBackend> VhostUserSlaveReqHandlerMut for DeviceRequestHandler<B
                 error!("invalid fd is given: {}", e);
                 VhostError::InvalidParam
             })?;
+
+            // Remove O_NONBLOCK from kick_fd. Otherwise, uring_executor will fails when we read
+            // values via `next_val()` later.
+            if let Err(e) = clear_fd_flags(rd, libc::O_NONBLOCK) {
+                error!("failed to remove O_NONBLOCK for kick fd: {}", e);
+                return Err(VhostError::InvalidParam);
+            }
+
             // Safe because the FD is now owned.
             let kick_evt = unsafe { Event::from_raw_descriptor(rd) };