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diff --git a/vhost_rs/src/backend.rs b/vhost_rs/src/backend.rs
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+// 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.
+
+//! Common traits and structs for vhost-kern and vhost-user backend drivers.
+
+use super::Result;
+use std::os::unix::io::RawFd;
+use vmm_sys_util::eventfd::EventFd;
+
+/// Maximum number of memory regions supported.
+pub const VHOST_MAX_MEMORY_REGIONS: usize = 255;
+
+/// Vring/virtque configuration data.
+pub struct VringConfigData {
+    /// Maximum queue size supported by the driver.
+    pub queue_max_size: u16,
+    /// Actual queue size negotiated by the driver.
+    pub queue_size: u16,
+    /// Bitmask of vring flags.
+    pub flags: u32,
+    /// Descriptor table address.
+    pub desc_table_addr: u64,
+    /// Used ring buffer address.
+    pub used_ring_addr: u64,
+    /// Available ring buffer address.
+    pub avail_ring_addr: u64,
+    /// Optional address for logging.
+    pub log_addr: Option<u64>,
+}
+
+/// Memory region configuration data.
+#[derive(Default, Clone, Copy)]
+pub struct VhostUserMemoryRegionInfo {
+    /// Guest physical address of the memory region.
+    pub guest_phys_addr: u64,
+    /// Size of the memory region.
+    pub memory_size: u64,
+    /// Virtual address in the current process.
+    pub userspace_addr: u64,
+    /// Optional offset where region starts in the mapped memory.
+    pub mmap_offset: u64,
+    /// Optional file diescriptor for mmap
+    pub mmap_handle: RawFd,
+}
+
+/// An interface for setting up vhost-based backend drivers.
+///
+/// Vhost-based virtio devices are different from regular virtio devices because the the vhost
+/// backend takes care of handling all the data transfer. The device itself only needs to deal with
+/// setting up the the backend driver and managing the control channel.
+pub trait VhostBackend: std::marker::Sized {
+    /// Get a bitmask of supported virtio/vhost features.
+    fn get_features(&mut self) -> Result<u64>;
+
+    /// Inform the vhost subsystem which features to enable.
+    /// This should be a subset of supported features from get_features().
+    ///
+    /// # Arguments
+    /// * `features` - Bitmask of features to set.
+    fn set_features(&mut self, features: u64) -> Result<()>;
+
+    /// Set the current process as the owner of the vhost backend.
+    /// This must be run before any other vhost commands.
+    fn set_owner(&mut self) -> Result<()>;
+
+    /// Used to be sent to request disabling all rings
+    /// This is no longer used.
+    fn reset_owner(&mut self) -> Result<()>;
+
+    /// Set the guest memory mappings for vhost to use.
+    fn set_mem_table(&mut self, regions: &[VhostUserMemoryRegionInfo]) -> Result<()>;
+
+    /// Set base address for page modification logging.
+    fn set_log_base(&mut self, base: u64, fd: Option<RawFd>) -> Result<()>;
+
+    /// Specify an eventfd file descriptor to signal on log write.
+    fn set_log_fd(&mut self, fd: RawFd) -> Result<()>;
+
+    /// Set the number of descriptors in the vring.
+    ///
+    /// # Arguments
+    /// * `queue_index` - Index of the queue to set descriptor count for.
+    /// * `num` - Number of descriptors in the queue.
+    fn set_vring_num(&mut self, queue_index: usize, num: u16) -> Result<()>;
+
+    /// Set the addresses for a given vring.
+    ///
+    /// # Arguments
+    /// * `queue_index` - Index of the queue to set addresses for.
+    /// * `config_data` - Configuration data for a vring.
+    fn set_vring_addr(&mut self, queue_index: usize, config_data: &VringConfigData) -> Result<()>;
+
+    /// Set the first index to look for available descriptors.
+    ///
+    /// # Arguments
+    /// * `queue_index` - Index of the queue to modify.
+    /// * `num` - Index where available descriptors start.
+    fn set_vring_base(&mut self, queue_index: usize, base: u16) -> Result<()>;
+
+    /// Get the available vring base offset.
+    fn get_vring_base(&mut self, queue_index: usize) -> Result<u32>;
+
+    /// Set the eventfd to trigger when buffers have been used by the host.
+    ///
+    /// # Arguments
+    /// * `queue_index` - Index of the queue to modify.
+    /// * `fd` - EventFd to trigger.
+    fn set_vring_call(&mut self, queue_index: usize, fd: &EventFd) -> Result<()>;
+
+    /// Set the eventfd that will be signaled by the guest when buffers are
+    /// available for the host to process.
+    ///
+    /// # Arguments
+    /// * `queue_index` - Index of the queue to modify.
+    /// * `fd` - EventFd that will be signaled from guest.
+    fn set_vring_kick(&mut self, queue_index: usize, fd: &sys_util::EventFd) -> Result<()>;
+
+    /// Set the eventfd that will be signaled by the guest when error happens.
+    ///
+    /// # Arguments
+    /// * `queue_index` - Index of the queue to modify.
+    /// * `fd` - EventFd that will be signaled from guest.
+    fn set_vring_err(&mut self, queue_index: usize, fd: &EventFd) -> Result<()>;
+}