Move trait VhostUserBackend to dedicated file

Move the VhostUserBackend trait to a dedicated file, preparing for
coming changes.

Signed-off-by: Liu Jiang <gerry@linux.alibaba.com>

src/backend.rs

@@ -0,0 +1,86 @@
+// Copyright 2019 Intel Corporation. All Rights Reserved.
+// Copyright 2019-2021 Alibaba Cloud. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
+use std::io;
+use std::result;
+use std::sync::{Arc, RwLock};
+
+use vhost::vhost_user::message::VhostUserProtocolFeatures;
+use vhost::vhost_user::SlaveFsCacheReq;
+use vm_memory::{GuestMemoryAtomic, GuestMemoryMmap};
+use vmm_sys_util::eventfd::EventFd;
+
+use super::Vring;
+
+/// This trait must be implemented by the caller in order to provide backend
+/// specific implementation.
+pub trait VhostUserBackend: Send + Sync + 'static {
+    /// Number of queues.
+    fn num_queues(&self) -> usize;
+
+    /// Depth of each queue.
+    fn max_queue_size(&self) -> usize;
+
+    /// Available virtio features.
+    fn features(&self) -> u64;
+
+    /// Acked virtio features.
+    fn acked_features(&mut self, _features: u64) {}
+
+    /// Virtio protocol features.
+    fn protocol_features(&self) -> VhostUserProtocolFeatures;
+
+    /// Tell the backend if EVENT_IDX has been negotiated.
+    fn set_event_idx(&mut self, enabled: bool);
+
+    /// Update guest memory regions.
+    fn update_memory(
+        &mut self,
+        atomic_mem: GuestMemoryAtomic<GuestMemoryMmap>,
+    ) -> result::Result<(), io::Error>;
+
+    /// This function gets called if the backend registered some additional
+    /// listeners onto specific file descriptors. The library can handle
+    /// virtqueues on its own, but does not know what to do with events
+    /// happening on custom listeners.
+    fn handle_event(
+        &self,
+        device_event: u16,
+        evset: epoll::Events,
+        vrings: &[Arc<RwLock<Vring>>],
+        thread_id: usize,
+    ) -> result::Result<bool, io::Error>;
+
+    /// Get virtio device configuration.
+    /// A default implementation is provided as we cannot expect all backends
+    /// to implement this function.
+    fn get_config(&self, _offset: u32, _size: u32) -> Vec<u8> {
+        Vec::new()
+    }
+
+    /// Set virtio device configuration.
+    /// A default implementation is provided as we cannot expect all backends
+    /// to implement this function.
+    fn set_config(&mut self, _offset: u32, _buf: &[u8]) -> result::Result<(), io::Error> {
+        Ok(())
+    }
+
+    /// Provide an exit EventFd
+    /// When this EventFd is written to the worker thread will exit. An optional id may
+    /// also be provided, if it not provided then the exit event will be first event id
+    /// after the last queue
+    fn exit_event(&self, _thread_index: usize) -> Option<(EventFd, Option<u16>)> {
+        None
+    }
+
+    /// Set slave fd.
+    /// A default implementation is provided as we cannot expect all backends
+    /// to implement this function.
+    fn set_slave_req_fd(&mut self, _vu_req: SlaveFsCacheReq) {}
+
+    fn queues_per_thread(&self) -> Vec<u64> {
+        vec![0xffff_ffff]
+    }
+}

src/lib.rs

@@ -34,6 +34,9 @@ use vm_memory::{
 };
 use vmm_sys_util::eventfd::EventFd;
 
+mod backend;
+pub use backend::VhostUserBackend;
+
 const MAX_MEM_SLOTS: u64 = 32;
 
 #[derive(Debug)]
@@ -62,77 +65,6 @@ pub enum Error {
 /// Result of vhost-user daemon operations.
 pub type Result<T> = result::Result<T, Error>;
 
-/// This trait must be implemented by the caller in order to provide backend
-/// specific implementation.
-pub trait VhostUserBackend: Send + Sync + 'static {
-    /// Number of queues.
-    fn num_queues(&self) -> usize;
-
-    /// Depth of each queue.
-    fn max_queue_size(&self) -> usize;
-
-    /// Available virtio features.
-    fn features(&self) -> u64;
-
-    /// Acked virtio features.
-    fn acked_features(&mut self, _features: u64) {}
-
-    /// Virtio protocol features.
-    fn protocol_features(&self) -> VhostUserProtocolFeatures;
-
-    /// Tell the backend if EVENT_IDX has been negotiated.
-    fn set_event_idx(&mut self, enabled: bool);
-
-    /// Update guest memory regions.
-    fn update_memory(
-        &mut self,
-        atomic_mem: GuestMemoryAtomic<GuestMemoryMmap>,
-    ) -> result::Result<(), io::Error>;
-
-    /// This function gets called if the backend registered some additional
-    /// listeners onto specific file descriptors. The library can handle
-    /// virtqueues on its own, but does not know what to do with events
-    /// happening on custom listeners.
-    fn handle_event(
-        &self,
-        device_event: u16,
-        evset: epoll::Events,
-        vrings: &[Arc<RwLock<Vring>>],
-        thread_id: usize,
-    ) -> result::Result<bool, io::Error>;
-
-    /// Get virtio device configuration.
-    /// A default implementation is provided as we cannot expect all backends
-    /// to implement this function.
-    fn get_config(&self, _offset: u32, _size: u32) -> Vec<u8> {
-        Vec::new()
-    }
-
-    /// Set virtio device configuration.
-    /// A default implementation is provided as we cannot expect all backends
-    /// to implement this function.
-    fn set_config(&mut self, _offset: u32, _buf: &[u8]) -> result::Result<(), io::Error> {
-        Ok(())
-    }
-
-    /// Provide an exit EventFd
-    /// When this EventFd is written to the worker thread will exit. An optional id may
-    /// also be provided, if it not provided then the exit event will be first event id
-    /// after the last queue
-    fn exit_event(&self, _thread_index: usize) -> Option<(EventFd, Option<u16>)> {
-        None
-    }
-
-    /// Set slave fd.
-    /// A default implementation is provided as we cannot expect all backends
-    /// to implement this function.
-    fn set_slave_req_fd(&mut self, _vu_req: SlaveFsCacheReq) {}
-
-    fn queues_per_thread(&self) -> Vec<u64> {
-        vec![0xffff_ffff]
-    }
-}
-
 /// This structure is the public API the backend is allowed to interact with
 /// in order to run a fully functional vhost-user daemon.
 pub struct VhostUserDaemon<S: VhostUserBackend> {