vm-virtio: Add vhost-user-net implementation

vhost-user framwork could provide good performance in data intensive
scenario due to the memory sharing mechanism. Implement vhost-user-net
device to get the benefit for Rust-based VMMs network.

Signed-off-by: Cathy Zhang <cathy.zhang@intel.com>

vm-virtio/src/vhost_user/mod.rs

@@ -0,0 +1,87 @@
+// Copyright 2019 Intel Corporation. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+extern crate epoll;
+extern crate net_util;
+extern crate vhost_rs;
+extern crate virtio_bindings;
+extern crate vm_memory;
+
+use std;
+use std::io;
+use vhost_rs::Error as VhostError;
+use vm_memory::Error as MmapError;
+
+mod handler;
+pub mod net;
+pub mod vu_common_ctrl;
+
+pub use self::net::Net;
+pub use self::vu_common_ctrl::VhostUserConfig;
+
+#[derive(Debug)]
+pub enum Error {
+    /// Invalid available address.
+    AvailAddress,
+    /// Queue number  is not correct
+    BadQueueNum,
+    /// Creating kill eventfd failed.
+    CreateKillEventFd(io::Error),
+    /// Cloning kill eventfd failed.
+    CloneKillEventFd(io::Error),
+    /// Invalid descriptor table address.
+    DescriptorTableAddress,
+    /// Create Epoll eventfd failed
+    EpollCreateFd(io::Error),
+    /// Epoll ctl error
+    EpollCtl(io::Error),
+    /// Epoll wait error
+    EpollWait(io::Error),
+    /// Read queue failed.
+    FailedReadingQueue(io::Error),
+    /// Signal used queue failed.
+    FailedSignalingUsedQueue(io::Error),
+    /// Failed to read vhost eventfd.
+    MemoryRegions(MmapError),
+    /// Failed to create master.
+    VhostUserCreateMaster(VhostError),
+    /// Failed to open vhost device.
+    VhostUserOpen(VhostError),
+    /// Get features failed.
+    VhostUserGetFeatures(VhostError),
+    /// Get protocol features failed.
+    VhostUserGetProtocolFeatures(VhostError),
+    /// Vhost-user Backend not support vhost-user protocol.
+    VhostUserProtocolNotSupport,
+    /// Set owner failed.
+    VhostUserSetOwner(VhostError),
+    /// Set features failed.
+    VhostUserSetFeatures(VhostError),
+    /// Set protocol features failed.
+    VhostUserSetProtocolFeatures(VhostError),
+    /// Set mem table failed.
+    VhostUserSetMemTable(VhostError),
+    /// Set vring num failed.
+    VhostUserSetVringNum(VhostError),
+    /// Set vring addr failed.
+    VhostUserSetVringAddr(VhostError),
+    /// Set vring base failed.
+    VhostUserSetVringBase(VhostError),
+    /// Set vring call failed.
+    VhostUserSetVringCall(VhostError),
+    /// Set vring kick failed.
+    VhostUserSetVringKick(VhostError),
+    /// Set vring enable failed.
+    VhostUserSetVringEnable(VhostError),
+    /// Vhost-user setup vring failed.
+    VhostUserSetupVringFailed,
+    /// Failed to create vhost eventfd.
+    VhostIrqCreate(io::Error),
+    /// Failed to read vhost eventfd.
+    VhostIrqRead(io::Error),
+    /// Failed to read vhost eventfd.
+    VhostUserMemoryRegion(MmapError),
+    /// Invalid used address.
+    UsedAddress,
+}
+type Result<T> = std::result::Result<T, Error>;