hypervisor: Extend hypervisor crate with Device trait

Added Device trait and KvmDevice struct for KVM-emulated devices.

Signed-off-by: Michael Zhao <michael.zhao@arm.com>

hypervisor/src/device.rs

@@ -0,0 +1,39 @@
+// Copyright © 2019 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0 OR BSD-3-Clause
+//
+// Copyright © 2020, Microsoft Corporation
+//
+// Copyright 2018-2019 CrowdStrike, Inc.
+//
+// Copyright 2020, ARM Limited
+//
+
+use crate::DeviceAttr;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+///
+/// Enum for device error
+pub enum HypervisorDeviceError {
+    ///
+    /// Set device attribute error
+    ///
+    #[error("Failed to set device attribute: {0}")]
+    SetDeviceAttribute(#[source] anyhow::Error),
+}
+
+///
+/// Result type for returning from a function
+///
+pub type Result<T> = std::result::Result<T, HypervisorDeviceError>;
+
+///
+/// Trait to represent a device
+///
+/// This crate provides a hypervisor-agnostic interfaces for device
+///
+pub trait Device: Send + Sync {
+    /// Set device attribute.
+    fn set_device_attr(&self, attr: &DeviceAttr) -> Result<()>;
+}