Use mio to replace Epoll

Epoll is linux-specific. So we use mio, which is a cross-platform
event notification, to replace Epoll.

Signed-off-by: Wenyu Huang <huangwenyuu@outlook.com>

Author: uran0sH

vhost-user-backend/CHANGELOG.md

@@ -6,6 +6,8 @@
 - [[#339]](https://github.com/rust-vmm/vhost/pull/339) Add support for `GET_SHMEM_CONFIG` message
 
 ### Changed
+- [[316](https://github.com/rust-vmm/vhost/pull/316)] Use mio to replace Epoll. Expose event_loop::EventSet.
+
 ### Deprecated
 ### Fixed
 

vhost-user-backend/Cargo.toml

@@ -20,6 +20,7 @@ postcopy = ["vhost/postcopy", "userfaultfd"]
 libc = "0.2.39"
 log = "0.4.17"
 userfaultfd = { version = "0.9.0", optional = true }
+mio = { version = "1.0.4", features = ["os-poll", "os-ext"] }
 vhost = { path = "../vhost", version = "0.15.0", features = ["vhost-user-backend"] }
 virtio-bindings = { workspace = true }
 virtio-queue = { workspace = true }

vhost-user-backend/src/backend.rs

@@ -29,14 +29,15 @@ use vhost::vhost_user::message::{
 };
 use vhost::vhost_user::Backend;
 use vm_memory::bitmap::Bitmap;
-use vmm_sys_util::epoll::EventSet;
 use vmm_sys_util::event::{EventConsumer, EventNotifier};
 
 use vhost::vhost_user::GpuBackend;
 
 use super::vring::VringT;
 use super::GM;
 
+use crate::EventSet;
+
 /// Trait with interior mutability for vhost user backend servers to implement concrete services.
 ///
 /// To support multi-threading and asynchronous IO, we enforce `Send + Sync` bound.
@@ -828,7 +829,7 @@ pub mod tests {
 
         let vring = VringRwLock::new(mem, 0x1000).unwrap();
         backend
-            .handle_event(0x1, EventSet::IN, &[vring], 0)
+            .handle_event(0x1, EventSet::Readable, &[vring], 0)
             .unwrap();
 
         backend.reset_device();