From c62227803047d0bf81279cb4aadcf131a194426d Mon Sep 17 00:00:00 2001
From: Rob Bradford <robert.bradford@intel.com>
Date: Tue, 17 Nov 2020 17:11:53 +0000
Subject: [PATCH] config, device_manager: Add support for disabling io_uring
 for testing

Add config parameter to --disk called "_disable_io_uring" (the
underscore prefix indicating it is not for public consumpion.) Use this
option to disable io_uring if it would otherwise be used.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
---
 vmm/src/config.rs         | 13 ++++++++++++-
 vmm/src/device_manager.rs |  2 +-
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/vmm/src/config.rs b/vmm/src/config.rs
index a6c81e32d..22fbcf2cd 100644
--- a/vmm/src/config.rs
+++ b/vmm/src/config.rs
@@ -622,6 +622,9 @@ pub struct DiskConfig {
     pub poll_queue: bool,
     #[serde(default)]
     pub id: Option<String>,
+    // For testing use only. Not exposed in API.
+    #[serde(default)]
+    pub disable_io_uring: bool,
 }
 
 fn default_diskconfig_num_queues() -> usize {
@@ -649,6 +652,7 @@ impl Default for DiskConfig {
             vhost_socket: None,
             poll_queue: default_diskconfig_poll_queue(),
             id: None,
+            disable_io_uring: false,
         }
     }
 }
@@ -671,7 +675,8 @@ impl DiskConfig {
             .add("vhost_user")
             .add("socket")
             .add("poll_queue")
-            .add("id");
+            .add("id")
+            .add("_disable_io_uring");
         parser.parse(disk).map_err(Error::ParseDisk)?;
 
         let path = parser.get("path").map(PathBuf::from);
@@ -710,6 +715,11 @@ impl DiskConfig {
             .unwrap_or_else(|| Toggle(default_diskconfig_poll_queue()))
             .0;
         let id = parser.get("id");
+        let disable_io_uring = parser
+            .convert::<Toggle>("_disable_io_uring")
+            .map_err(Error::ParseDisk)?
+            .unwrap_or(Toggle(false))
+            .0;
 
         if parser.is_set("poll_queue") && !vhost_user {
             warn!("poll_queue parameter currently only has effect when used vhost_user=true");
@@ -726,6 +736,7 @@ impl DiskConfig {
             vhost_user,
             poll_queue,
             id,
+            disable_io_uring,
         })
     }
 }
diff --git a/vmm/src/device_manager.rs b/vmm/src/device_manager.rs
index 9bc366d5b..c18b83a6e 100644
--- a/vmm/src/device_manager.rs
+++ b/vmm/src/device_manager.rs
@@ -1642,7 +1642,7 @@ impl DeviceManager {
                 ImageType::Raw => {
                     // Use asynchronous backend relying on io_uring if the
                     // syscalls are supported.
-                    if block_io_uring_is_supported() {
+                    if block_io_uring_is_supported() && !disk_cfg.disable_io_uring {
                         let dev = Arc::new(Mutex::new(
                             virtio_devices::BlockIoUring::new(
                                 id.clone(),