vhost_rs: Copy vhost crate from jiangliu/v1

In order to avoid cloud-hypervisor to rely on a pending PR for the empty
crate "vhost", this commit temporarily copies the content of the crate
based on branch jiangliu/v1 18b5081d9199c76eca49da1971c9d1a65e53e5ff.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vhost_rs/src/lib.rs

@@ -0,0 +1,120 @@
+// Copyright (C) 2019 Alibaba Cloud Computing. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+//
+// Portions Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+//
+// Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE-BSD file.
+
+//! Virtio Vhost Backend Drivers
+//!
+//! Virtio devices use virtqueues to transport data efficiently. Virtqueue is a set of three
+//! different single-producer, single-consumer ring structures designed to store generic
+//! scatter-gather I/O.
+//!
+//! Vhost is a mechanism to improve performance of Virtio devices by delegate data plane operations
+//! to dedicated IO service processes. Only the configuration, I/O submission notification, and I/O
+//! completion interruption are piped through the hypervisor.
+//! It uses the same virtqueue layout as Virtio to allow Vhost devices to be mapped directly to
+//! Virtio devices. This allows a Vhost device to be accessed directly by a guest OS inside a
+//! hypervisor process with an existing Virtio (PCI) driver.
+//!
+//! The initial vhost implementation is a part of the Linux kernel and uses ioctl interface to
+//! communicate with userspace applications. Dedicated kernel worker threads are created to handle
+//! IO requests from the guest.
+//!
+//! Later Vhost-user protocol is introduced to complement the ioctl interface used to control the
+//! vhost implementation in the Linux kernel. It implements the control plane needed to establish
+//! virtqueues sharing with a user space process on the same host. It uses communication over a
+//! Unix domain socket to share file descriptors in the ancillary data of the message.
+//! The protocol defines 2 sides of the communication, master and slave. Master is the application
+//! that shares its virtqueues. Slave is the consumer of the virtqueues. Master and slave can be
+//! either a client (i.e. connecting) or server (listening) in the socket communication.
+
+#![deny(missing_docs)]
+
+#[cfg_attr(
+    any(feature = "vhost-user-master", feature = "vhost-user-slave"),
+    macro_use
+)]
+extern crate bitflags;
+extern crate libc;
+#[cfg(feature = "vhost-kern")]
+extern crate vm_memory;
+#[cfg_attr(feature = "vhost-kern", macro_use)]
+extern crate vmm_sys_util;
+
+mod backend;
+pub use backend::*;
+
+#[cfg(feature = "vhost-kern")]
+pub mod vhost_kern;
+#[cfg(any(feature = "vhost-user-master", feature = "vhost-user-slave"))]
+pub mod vhost_user;
+#[cfg(feature = "vhost-vsock")]
+pub mod vsock;
+
+/// Error codes for vhost operations
+#[derive(Debug)]
+pub enum Error {
+    /// Invalid operations.
+    InvalidOperation,
+    /// Invalid guest memory.
+    InvalidGuestMemory,
+    /// Invalid guest memory region.
+    InvalidGuestMemoryRegion,
+    /// Invalid queue.
+    InvalidQueue,
+    /// Invalid descriptor table address.
+    DescriptorTableAddress,
+    /// Invalid used address.
+    UsedAddress,
+    /// Invalid available address.
+    AvailAddress,
+    /// Invalid log address.
+    LogAddress,
+    #[cfg(feature = "vhost-kern")]
+    /// Error opening the vhost backend driver.
+    VhostOpen(std::io::Error),
+    #[cfg(feature = "vhost-kern")]
+    /// Error while running ioctl.
+    IoctlError(std::io::Error),
+    /// Error from IO subsystem.
+    IOError(std::io::Error),
+    #[cfg(any(feature = "vhost-user-master", feature = "vhost-user-slave"))]
+    /// Error from the vhost-user subsystem.
+    VhostUserProtocol(vhost_user::Error),
+}
+
+impl std::fmt::Display for Error {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Error::InvalidOperation => write!(f, "invalid vhost operations"),
+            Error::InvalidGuestMemory => write!(f, "invalid guest memory object"),
+            Error::InvalidGuestMemoryRegion => write!(f, "invalid guest memory region"),
+            Error::InvalidQueue => write!(f, "invalid virtque"),
+            Error::DescriptorTableAddress => write!(f, "invalid virtque descriptor talbe address"),
+            Error::UsedAddress => write!(f, "invalid virtque used talbe address"),
+            Error::AvailAddress => write!(f, "invalid virtque available talbe address"),
+            Error::LogAddress => write!(f, "invalid virtque log address"),
+            Error::IOError(e) => write!(f, "IO error: {}", e),
+            #[cfg(feature = "vhost-kern")]
+            Error::VhostOpen(e) => write!(f, "failure in opening vhost file: {}", e),
+            #[cfg(feature = "vhost-kern")]
+            Error::IoctlError(e) => write!(f, "failure in vhost ioctl: {}", e),
+            #[cfg(any(feature = "vhost-user-master", feature = "vhost-user-slave"))]
+            Error::VhostUserProtocol(e) => write!(f, "vhost-user: {}", e),
+        }
+    }
+}
+
+#[cfg(any(feature = "vhost-user-master", feature = "vhost-user-slave"))]
+impl std::convert::From<vhost_user::Error> for Error {
+    fn from(err: vhost_user::Error) -> Self {
+        Error::VhostUserProtocol(err)
+    }
+}
+
+/// Result of vhost operations
+pub type Result<T> = std::result::Result<T, Error>;