Add core VhostUserDevice implementation

Implement generic vhost-user device wrapper
with connection, feature negotiation, and
Guest physical address(GPA) to Virtual
address(VA) translation. Supports protocol
feature negotiation (CONFIG, MQ) and forwards
backend interrupts to guest.

Signed-off-by: Dorinda Bassey <dbassey@redhat.com>

Author: Dorinda Bassey

src/devices/src/virtio/mod.rs

@@ -36,6 +36,8 @@ mod queue;
 pub mod rng;
 #[cfg(feature = "snd")]
 pub mod snd;
+#[cfg(feature = "vhost-user")]
+pub mod vhost_user;
 pub mod vsock;
 
 #[cfg(not(feature = "tee"))]
@@ -56,6 +58,8 @@ pub use self::queue::{Descriptor, DescriptorChain, Queue};
 pub use self::rng::*;
 #[cfg(feature = "snd")]
 pub use self::snd::Snd;
+#[cfg(feature = "vhost-user")]
+pub use self::vhost_user::VhostUserDevice;
 pub use self::vsock::*;
 
 /// When the driver initializes the device, it lets the device know about the