Vhost-user-console device and can license fixes

This patch presents a new console device and fixes vhost-user-can
license.
vhost-device can and conosle devices will be proposed to
rust-vmm/vhost-device community, and in case of acceptace this patch
will be updated.

Bug-AGL: SPEC-4834

Change-Id: I4dcded8733195158f848bd0e4fd4f4618a378c3a
Signed-off-by: Michele Paolino <m.paolino@virtualopensystems.com>

4 files changed, 1109 insertions, 0 deletions

diff --git a/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/backend.rs b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/backend.rs
new file mode 100644
index 00000000..15b50a38
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/backend.rs
@@ -0,0 +1,211 @@
+// VIRTIO CONSOLE Emulation via vhost-user
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+use log::{error, info, warn};
+use std::process::exit;
+use std::sync::{Arc, RwLock};
+use std::thread::{spawn, JoinHandle};
+
+use clap::Parser;
+use thiserror::Error as ThisError;
+use vhost::{vhost_user, vhost_user::Listener};
+use vhost_user_backend::VhostUserDaemon;
+use vm_memory::{GuestMemoryAtomic, GuestMemoryMmap};
+
+use crate::console::{ConsoleController};
+use crate::vhu_console::VhostUserConsoleBackend;
+
+pub(crate) type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug, ThisError)]
+/// Errors related to low level Console helpers
+pub(crate) enum Error {
+    #[error("Invalid socket count: {0}")]
+    SocketCountInvalid(usize),
+    #[error("Failed to join threads")]
+    FailedJoiningThreads,
+    #[error("Could not create console controller: {0}")]
+    CouldNotCreateConsoleController(crate::console::Error),
+    #[error("Could not create console backend: {0}")]
+    CouldNotCreateBackend(crate::vhu_console::Error),
+    #[error("Could not create daemon: {0}")]
+    CouldNotCreateDaemon(vhost_user_backend::Error),
+}
+
+#[derive(Parser, Debug)]
+#[clap(author, version, about, long_about = None)]
+struct ConsoleArgs {
+    /// Location of vhost-user Unix domain socket. This is suffixed by 0,1,2..socket_count-1.
+    #[clap(short, long)]
+    socket_path: String,
+
+    /// A console device name to be used for reading (ex. vconsole, console0, console1, ... etc.)
+    #[clap(short = 'i', long)]
+    console_path: String,
+
+    /// Number of guests (sockets) to connect to.
+    #[clap(short = 'c', long, default_value_t = 1)]
+    socket_count: u32,
+}
+
+#[derive(PartialEq, Debug)]
+struct ConsoleConfiguration {
+    socket_path: String,
+    socket_count: u32,
+    console_path: String,
+}
+
+impl TryFrom<ConsoleArgs> for ConsoleConfiguration {
+    type Error = Error;
+
+    fn try_from(args: ConsoleArgs) -> Result<Self> {
+
+        if args.socket_count == 0 {
+            return Err(Error::SocketCountInvalid(0));
+        }
+
+		let console_path = args.console_path.trim().to_string();
+
+        Ok(ConsoleConfiguration {
+            socket_path: args.socket_path,
+			socket_count: args.socket_count,
+            console_path,
+        })
+    }
+}
+
+fn start_backend(args: ConsoleArgs) -> Result<()> {
+
+	println!("start_backend function!\n");
+
+    let config = ConsoleConfiguration::try_from(args).unwrap();
+    let mut handles = Vec::new();
+
+    for _ in 0..config.socket_count {
+        let socket = config.socket_path.to_owned();
+        let console_path = config.console_path.to_owned();
+
+        let handle: JoinHandle<Result<()>> = spawn(move || loop {
+            // A separate thread is spawned for each socket and console connect to a separate guest.
+            // These are run in an infinite loop to not require the daemon to be restarted once a
+            // guest exits.
+            //
+            // There isn't much value in complicating code here to return an error from the
+            // threads, and so the code uses unwrap() instead. The panic on a thread won't cause
+            // trouble to other threads/guests or the main() function and should be safe for the
+            // daemon.
+
+            let controller =
+                ConsoleController::new(console_path.clone()).map_err(Error::CouldNotCreateConsoleController)?;
+			let arc_controller =  Arc::new(RwLock::new(controller));
+            let vu_console_backend = Arc::new(RwLock::new(
+                VhostUserConsoleBackend::new(arc_controller).map_err(Error::CouldNotCreateBackend)?,
+            ));
+
+            let mut daemon = VhostUserDaemon::new(
+                String::from("vhost-device-console-backend"),
+                vu_console_backend.clone(),
+                GuestMemoryAtomic::new(GuestMemoryMmap::new()),
+            )
+            .map_err(Error::CouldNotCreateDaemon)?;
+
+            /* Start the read thread -- need to handle it after termination */
+            let vring_workers = daemon.get_epoll_handlers();
+            vu_console_backend.read()
+                          .unwrap()
+                          .set_vring_worker(&vring_workers[0]);
+			VhostUserConsoleBackend::start_console_thread(&vu_console_backend);
+
+            let listener = Listener::new(socket.clone(), true).unwrap();
+            daemon.start(listener).unwrap();
+
+            match daemon.wait() {
+                Ok(()) => {
+                    info!("Stopping cleanly.");
+                }
+                Err(vhost_user_backend::Error::HandleRequest(
+                    vhost_user::Error::PartialMessage | vhost_user::Error::Disconnected,
+                )) => {
+                    info!("vhost-user connection closed with partial message. If the VM is shutting down, this is expected behavior; otherwise, it might be a bug.");
+                }
+                Err(e) => {
+                    warn!("Error running daemon: {:?}", e);
+                }
+            }
+
+            // No matter the result, we need to shut down the worker thread.
+            vu_console_backend.read().unwrap().exit_event.write(1).unwrap();
+        });
+
+        handles.push(handle);
+    }
+
+    for handle in handles {
+        handle.join().map_err(|_| Error::FailedJoiningThreads)??;
+    }
+
+    Ok(())
+}
+
+pub(crate) fn console_init() {
+    env_logger::init();
+	println!("Console_init function!");
+    if let Err(e) = start_backend(ConsoleArgs::parse()) {
+        error!("{e}");
+        exit(1);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_console_configuration_try_from_valid_args() {
+        let args = ConsoleArgs {
+            socket_path: String::from("/path/to/socket"),
+            console_path: String::from("vconsole"),
+            socket_count: 3,
+        };
+
+        let result = ConsoleConfiguration::try_from(args);
+
+        assert!(result.is_ok());
+
+        let config = result.unwrap();
+        assert_eq!(config.socket_path, "/path/to/socket");
+        assert_eq!(config.console_path, "vconsole");
+        assert_eq!(config.socket_count, 3);
+    }
+
+    #[test]
+    fn test_console_configuration_try_from_invalid_args() {
+        // Test with socket_count = 0
+        let args_invalid_count = ConsoleArgs {
+            socket_path: String::from("/path/to/socket"),
+            console_path: String::from("vconsole"),
+            socket_count: 0,
+        };
+
+        let result_invalid_count = ConsoleConfiguration::try_from(args_invalid_count);
+        assert!(result_invalid_count.is_err());
+    }
+
+    #[test]
+    fn test_start_backend_success() {
+        // Test start_backend with valid arguments
+        let args = ConsoleArgs {
+            socket_path: String::from("/path/to/socket"),
+            console_path: String::from("vconsole"),
+            socket_count: 2,
+        };
+
+        let result = start_backend(args);
+
+        assert!(result.is_ok());
+    }
+}
diff --git a/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/console.rs b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/console.rs
new file mode 100644
index 00000000..2e2972b2
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/console.rs
@@ -0,0 +1,86 @@
+// CAN backend device
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+use log::{warn, error};
+use std::sync::{Arc, RwLock};
+
+use thiserror::Error as ThisError;
+use vm_memory::{ByteValued, Le16};
+
+use crate::vhu_console::{VirtioConsoleConfig, VirtioConsoleControl};
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Copy, Clone, Debug, PartialEq, ThisError)]
+pub(crate) enum Error {
+    #[error("Console not enabled yet")]
+    ConsoleNotEnabled,
+}
+
+#[derive(Debug)]
+pub(crate) struct ConsoleController {
+    config: VirtioConsoleConfig,
+    pub console_name: String,
+}
+
+impl ConsoleController {
+    // Creates a new controller corresponding to `device`.
+    pub(crate) fn new(console_name: String) -> Result<ConsoleController> {
+
+        let console_name = console_name.to_owned();
+		println!("console_name: {:?}", console_name);
+
+        Ok(ConsoleController {
+            config: VirtioConsoleConfig {
+						cols: 20.into(),
+						rows: 20.into(),
+						max_nr_ports: 1.into(),
+						emerg_wr: 64.into(),
+					},
+            console_name,
+        })
+    }
+
+    pub(crate) fn config(&self) -> &VirtioConsoleConfig {
+		log::trace!("Get config\n");
+        &self.config
+    }
+
+    pub(crate) fn operation(&self, tx_request: VirtioConsoleControl) -> Result<()> {
+		log::trace!("Console operation\n");
+		Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_new_console_controller() {
+        let console_name = String::from("test_console");
+        let controller = ConsoleController::new(console_name.clone());
+
+        assert!(controller.is_ok());
+
+        let controller = controller.unwrap();
+        assert_eq!(controller.console_name, "test_console");
+    }
+
+    #[test]
+    fn test_console_controller_config() {
+        let console_name = String::from("test_console");
+        let controller = ConsoleController::new(console_name).unwrap();
+
+        let config = controller.config();
+        assert_eq!(config.cols, 20);
+        assert_eq!(config.rows, 20);
+        assert_eq!(config.max_nr_ports, 1);
+        assert_eq!(config.emerg_wr, 64);
+    }
+}
+
diff --git a/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/main.rs b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/main.rs
new file mode 100644
index 00000000..cceafb4f
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/main.rs
@@ -0,0 +1,18 @@
+// VIRTIO CONSOLE Emulation via vhost-user
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+#[cfg(target_env = "gnu")]
+mod backend;
+#[cfg(target_env = "gnu")]
+mod console;
+#[cfg(target_env = "gnu")]
+mod vhu_console;
+
+#[cfg(target_env = "gnu")]
+fn main() {
+    backend::console_init()
+}
diff --git a/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/vhu_console.rs b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/vhu_console.rs
new file mode 100644
index 00000000..ebddb00d
--- /dev/null
+++ b/meta-egvirt/recipes-extended/vhost-device-console/vhost-device-console-0.1.0/src/vhu_console.rs
@@ -0,0 +1,794 @@
+// vhost device console
+//
+// Copyright 2023 VIRTUAL OPEN SYSTEMS SAS. All Rights Reserved.
+//          Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
+//
+// SPDX-License-Identifier: Apache-2.0 or BSD-3-Clause
+
+use log::{warn, error};
+use std::mem::size_of;
+use std::slice::from_raw_parts;
+use std::sync::{Arc, RwLock};
+use std::{
+    convert,
+    io::{self, Result as IoResult},
+};
+use std::io::{Write};
+use std::os::fd::AsRawFd;
+use thiserror::Error as ThisError;
+use vhost::vhost_user::message::{VhostUserProtocolFeatures, VhostUserVirtioFeatures};
+use vhost_user_backend::{VhostUserBackendMut, VringRwLock, VringT};
+use virtio_bindings::bindings::virtio_config::{VIRTIO_F_NOTIFY_ON_EMPTY, VIRTIO_F_VERSION_1};
+use virtio_bindings::bindings::virtio_ring::{
+    VIRTIO_RING_F_EVENT_IDX, VIRTIO_RING_F_INDIRECT_DESC,
+};
+use virtio_queue::{DescriptorChain, QueueOwnedT};
+use vm_memory::{
+    ByteValued, Bytes, GuestAddressSpace, GuestMemoryAtomic, GuestMemoryLoadGuard,
+    GuestMemoryMmap, Le16, Le32,
+};
+use vmm_sys_util::epoll::EventSet;
+use vmm_sys_util::eventfd::{EventFd, EFD_NONBLOCK};
+use vhost_user_backend::VringEpollHandler;
+use crate::console::{ConsoleController};
+
+use std::thread::{JoinHandle, spawn};
+use queues::{Queue, IsQueue};
+use std::thread;
+use std::time::Duration;
+use console::Term;
+
+/// Feature bit numbers
+pub const VIRTIO_CONSOLE_F_SIZE: u16 = 0;
+pub const VIRTIO_CONSOLE_F_MULTIPORT: u16 = 1;
+pub const VIRTIO_CONSOLE_F_EMERG_WRITE: u16 = 2;
+
+/// Virtio configuration
+const QUEUE_SIZE: usize = 128;
+const NUM_QUEUES: usize = 4;
+
+/// Queues
+const RX_QUEUE: u16 = 0;
+const TX_QUEUE: u16 = 1;
+const CTRL_RX_QUEUE: u16 = 2;
+const CTRL_TX_QUEUE: u16 = 3;
+const BACKEND_EFD: u16 = (NUM_QUEUES + 1) as u16;
+const BACKEND_RX_EFD: u16 = (NUM_QUEUES + 2) as u16;
+
+
+/// Console virtio control messages
+const VIRTIO_CONSOLE_DEVICE_READY: u16 = 0 ;
+const VIRTIO_CONSOLE_PORT_ADD: u16 = 1;
+const VIRTIO_CONSOLE_PORT_REMOVE: u16 = 2; 
+const VIRTIO_CONSOLE_PORT_READY: u16 = 3;
+const VIRTIO_CONSOLE_CONSOLE_PORT: u16 = 4; 
+const VIRTIO_CONSOLE_RESIZE: u16 = 5;
+const VIRTIO_CONSOLE_PORT_OPEN: u16 = 6; 
+const VIRTIO_CONSOLE_PORT_NAME: u16 = 7;
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Copy, Clone, Debug, PartialEq, ThisError)]
+pub(crate) enum Error {
+    #[error("Failed to handle event, didn't match EPOLLIN")]
+    HandleEventNotEpollIn,
+    #[error("Failed to handle unknown event")]
+    HandleEventUnknown,
+    #[error("Received unexpected write only descriptor at index {0}")]
+    UnexpectedWriteOnlyDescriptor(usize),
+    #[error("Received unexpected readable descriptor at index {0}")]
+    UnexpectedReadableDescriptor(usize),
+    #[error("Invalid descriptor count {0}")]
+    UnexpectedDescriptorCount(usize),
+    #[error("Invalid descriptor size, expected: {0}, found: {1}")]
+    UnexpectedDescriptorSize(usize, u32),
+	#[error("Descriptor not found")]
+	DescriptorNotFound,
+	#[error("Failed to send notification")]
+	NotificationFailed,
+    #[error("Descriptor read failed")]
+    DescriptorReadFailed,
+    #[error("Descriptor write failed")]
+    DescriptorWriteFailed,
+    #[error("Failed to create new EventFd")]
+    EventFdFailed,
+    #[error("Failed to remove rx queue")]
+    EmptyQueue,
+}
+
+impl convert::From<Error> for io::Error {
+    fn from(e: Error) -> Self {
+        io::Error::new(io::ErrorKind::Other, e)
+    }
+}
+
+/// Virtio Console Config
+#[derive(Copy, Clone, Debug, Default, PartialEq)]
+#[repr(C)]
+pub(crate) struct VirtioConsoleConfig {
+    pub cols: Le16,
+    pub rows: Le16,
+    pub max_nr_ports: Le32,
+    pub emerg_wr: Le32,
+}
+
+// SAFETY: The layout of the structure is fixed and can be initialized by
+// reading its content from byte array.
+unsafe impl ByteValued for VirtioConsoleConfig {}
+
+#[derive(Copy, Clone, Debug, Default, PartialEq)]
+#[repr(C)]
+pub(crate) struct VirtioConsoleControl {
+    pub id: Le32,
+    pub event: Le16,
+    pub value: Le16,
+}
+
+use std::io::Cursor;
+
+impl VirtioConsoleControl {
+    fn to_le_bytes(&self) -> Vec<u8> {
+        let mut buffer = Vec::new();
+
+		buffer.extend_from_slice(&self.id.to_native().to_le_bytes());
+		buffer.extend_from_slice(&self.event.to_native().to_le_bytes());
+		buffer.extend_from_slice(&self.value.to_native().to_le_bytes());
+        buffer
+    }
+}
+
+// SAFETY: The layout of the structure is fixed and can be initialized by
+// reading its content from byte array.
+unsafe impl ByteValued for VirtioConsoleControl {}
+
+pub(crate) struct VhostUserConsoleBackend {
+    controller: Arc<RwLock<ConsoleController>>,
+	acked_features: u64,
+    event_idx: bool,
+	rx_fifo: Queue<VirtioConsoleControl>,
+    pub(crate) ready: bool,
+    pub(crate) ready_to_write: bool,
+	pub(crate) output_buffer: String,
+    pub(crate) rx_event: EventFd,
+    pub(crate) rx_ctrl_event: EventFd,
+    pub(crate) exit_event: EventFd,
+    mem: Option<GuestMemoryAtomic<GuestMemoryMmap>>,
+}
+
+type ConsoleDescriptorChain = DescriptorChain<GuestMemoryLoadGuard<GuestMemoryMmap<()>>>;
+
+impl VhostUserConsoleBackend {
+    pub(crate) fn new(controller: Arc<RwLock<ConsoleController>>) -> Result<Self> {
+        Ok(VhostUserConsoleBackend {
+            controller: controller,
+            event_idx: false,
+			rx_fifo: Queue::new(),
+			acked_features: 0x0,
+			ready: false,
+			ready_to_write: false,
+			output_buffer: String::new(),
+            rx_event: EventFd::new(EFD_NONBLOCK).map_err(|_| Error::EventFdFailed)?,
+            rx_ctrl_event: EventFd::new(EFD_NONBLOCK).map_err(|_| Error::EventFdFailed)?,
+            exit_event: EventFd::new(EFD_NONBLOCK).map_err(|_| Error::EventFdFailed)?,
+            mem: None,
+        })
+    }
+
+	fn check_features (&self, features: u16) -> bool {
+		(self.acked_features & (1 << features)) != 0
+	}
+
+    fn print_console_frame (&self, control_msg: VirtioConsoleControl) {
+        println!("id 0x{:x}", control_msg.id.to_native());
+        println!("event 0x{:x}", control_msg.event.to_native());
+        println!("value 0x{:x}", control_msg.value.to_native());
+    }
+
+    fn process_rx_requests(
+		&mut self,
+		requests: Vec<ConsoleDescriptorChain>,
+		vring: &VringRwLock
+	) -> Result<bool> {
+		log::trace!("process_rx_requests");
+
+        if requests.is_empty() {
+			log::trace!("requests.is_empty");
+			vring.signal_used_queue();
+            return Ok(true);
+        }
+
+		log::trace!("requests.len: {:?}", requests.len());
+        let desc_chain = &requests[0];
+        let descriptors: Vec<_> = desc_chain.clone().collect();
+
+		log::trace!("descriptors.len(): {:?}", descriptors.len());
+        if descriptors.len() != 1 {
+			log::trace!("Error::UnexpectedDescriptorCount");
+            return Err(Error::UnexpectedDescriptorCount(descriptors.len()));
+        }
+
+        let desc_request = descriptors[0];
+        if !desc_request.is_write_only() {
+			log::trace!("!desc_request.is_write_only()");
+            return Err(Error::UnexpectedReadableDescriptor(1));
+        }
+
+        // TODO: if buffer is more than the the desc_request length,
+        //       write the remaining in the next chain.
+		log::trace!("desc_request.len(): {}", desc_request.len());
+		let response = self.output_buffer.clone();
+
+        desc_chain
+            .memory()
+            .write_slice(response.as_bytes(), desc_request.addr())
+            .map_err(|_| Error::DescriptorWriteFailed)?;
+
+        if vring.add_used(desc_chain.head_index(), response.as_bytes().len() as u32).is_err() {
+            warn!("Couldn't return used descriptors to the ring");
+        }
+
+        Ok(true)
+    }
+
+    fn process_tx_requests(
+		&self,
+		requests: Vec<ConsoleDescriptorChain>,
+		vring: &VringRwLock
+	) -> Result<bool> {
+		log::trace!("process_tx_requests");
+
+        if requests.is_empty() {
+			log::trace!("requests.is_empty");
+            return Ok(true);
+        }
+
+		log::trace!("requests.len: {:?}", requests.len());
+        for desc_chain in requests {
+            let descriptors: Vec<_> = desc_chain.clone().collect();
+
+			log::trace!("descriptors.len(): {:?}", descriptors.len());
+            if descriptors.len() != 1 {
+				log::trace!("Error::UnexpectedDescriptorCount");
+                return Err(Error::UnexpectedDescriptorCount(descriptors.len()));
+            }
+
+            let desc_request = descriptors[0];
+            if desc_request.is_write_only() {
+				log::trace!("Error::UnexpectedReadOnlyDescriptor");
+                return Err(Error::UnexpectedWriteOnlyDescriptor(0));
+			}
+
+			log::trace!("desc_request.len(): {}", desc_request.len());
+			let desc_len = desc_request.len();
+
+			let mut buffer = [0 as u8; 4096];
+
+            let request = desc_chain
+                .memory()
+                .read_slice(&mut buffer, desc_request.addr())
+                .map_err(|_| Error::DescriptorReadFailed)?;
+
+			let new_buff = &buffer[0..desc_len as usize];
+
+		    let my_string = String::from_utf8(new_buff.to_vec()).unwrap();
+		    log::trace!("{}", my_string);
+		    print!("{}", my_string);
+    	    io::stdout().flush().unwrap(); // Ensure the prompt is displayed.
+
+            if vring.add_used(desc_chain.head_index(), desc_request.len()).is_err() {
+                log::trace!("Couldn't return used descriptors to the ring");
+                warn!("Couldn't return used descriptors to the ring");
+            }
+        }
+
+        Ok(true)
+    }
+
+    fn process_ctrl_rx_requests(
+		&mut self,
+		requests: Vec<ConsoleDescriptorChain>,
+		vring: &VringRwLock,
+	) -> Result<bool> {
+		log::trace!("process_ctrl_rx_requests");
+
+        if requests.is_empty() {
+			log::trace!("requests.is_empty()");
+            return Ok(true);
+        }
+		log::trace!("\trequests.len(): {}", requests.len());
+
+        for desc_chain in requests {
+
+			let descriptors: Vec<_> = desc_chain.clone().collect();
+
+			log::trace!("descriptors.len(): {:?}", descriptors.len());
+            if descriptors.len() < 1 {
+				warn!("Error::UnexpectedDescriptorCount");
+                return Err(Error::UnexpectedDescriptorCount(descriptors.len()));
+            }
+
+			log::trace!("self.rx_fifo.size(): {}", self.rx_fifo.size());
+			let ctrl_msg: VirtioConsoleControl = match self.rx_fifo.remove() {
+				Ok(item) => item,         
+				_ => {
+						log::trace!("No rx elements");
+						return Ok(false)
+					 },
+			};
+
+            let desc_request = descriptors[0];
+            if !desc_request.is_write_only() {
+				warn!("Error::UnexpectedWriteOnlyDescriptor");
+                return Err(Error::UnexpectedWriteOnlyDescriptor(0));
+            }
+
+            if (desc_request.len() as usize) < size_of::<VirtioConsoleControl>() {
+				log::trace!("UnexpectedDescriptorSize, len = {:?}", desc_request.len());
+                return Err(Error::UnexpectedDescriptorSize(
+                    size_of::<VirtioConsoleControl>(),
+                    desc_request.len(),
+                ));
+            }
+
+			log::trace!("desc_request.len(): {}", desc_request.len());
+			self.print_console_frame(ctrl_msg);
+
+		    let mut buffer: Vec<u8> = Vec::new();
+		    buffer.extend_from_slice(&ctrl_msg.to_le_bytes());
+		
+			if ctrl_msg.event.to_native() == VIRTIO_CONSOLE_PORT_NAME {
+		    	let string_bytes = "org.fedoraproject.console.foo!".as_bytes();
+		    	buffer.extend_from_slice(string_bytes);
+			};
+
+			desc_chain
+        	    .memory()
+        	    .write_slice(&buffer, desc_request.addr())
+        	    .map_err(|_| Error::DescriptorWriteFailed)?;
+
+            if vring.add_used(desc_chain.head_index(), desc_request.len()).is_err() {
+                log::trace!("Couldn't return used descriptors to the ring");
+                warn!("Couldn't return used descriptors to the ring");
+            }
+        }
+
+        Ok(true)
+    }
+
+	fn handle_control_msg (
+		&mut self,
+		vring: &VringRwLock,
+		ctrl_msg: VirtioConsoleControl
+	) -> Result<()> {
+
+		let mut ctrl_msg_reply = VirtioConsoleControl {
+								id: 0.into(),
+								event: 0.into(),
+								value: 1.into(),
+							};
+		match ctrl_msg.event.to_native() {
+			VIRTIO_CONSOLE_DEVICE_READY => {
+				log::trace!("VIRTIO_CONSOLE_DEVICE_READY");
+				self.ready = true;
+				ctrl_msg_reply.event = VIRTIO_CONSOLE_PORT_ADD.into();
+				self.rx_fifo.add(ctrl_msg_reply);
+				self.process_ctrl_rx_queue(vring)?;
+			},
+		    VIRTIO_CONSOLE_PORT_READY => {
+				log::trace!("VIRTIO_CONSOLE_PORT_READY");
+				ctrl_msg_reply.event = VIRTIO_CONSOLE_CONSOLE_PORT.into();
+				self.rx_fifo.add(ctrl_msg_reply.clone());
+				self.process_ctrl_rx_queue(vring)?;
+
+				ctrl_msg_reply.event = VIRTIO_CONSOLE_PORT_NAME.into();
+				self.rx_fifo.add(ctrl_msg_reply.clone());
+				self.process_ctrl_rx_queue(vring)?;
+
+				ctrl_msg_reply.event = VIRTIO_CONSOLE_PORT_OPEN.into();
+				self.rx_fifo.add(ctrl_msg_reply.clone());
+				self.process_ctrl_rx_queue(vring)?;
+			},
+		    VIRTIO_CONSOLE_PORT_OPEN => {
+				log::trace!("VIRTIO_CONSOLE_PORT_OPEN");
+			},
+		    _ => {
+				log::trace!("Uknown control event");
+				return Err(Error::HandleEventUnknown);
+			}
+		};
+        Ok(())
+	}
+
+    fn process_ctrl_tx_requests(
+		&mut self,
+		requests: Vec<ConsoleDescriptorChain>,
+		vring: &VringRwLock,
+		rx_ctrl_vring: &VringRwLock
+	) -> Result<bool> {
+		log::trace!("process_ctrl_tx_requests");
+
+        if requests.is_empty() {
+			log::trace!("requests.is_empty()");
+            return Ok(true);
+        }
+
+        for desc_chain in requests {
+			let descriptors: Vec<_> = desc_chain.clone().collect();
+
+            if descriptors.len() < 1 {
+				warn!("Error::UnexpectedDescriptorCount");
+                return Err(Error::UnexpectedDescriptorCount(descriptors.len()));
+            }
+
+			log::trace!("descriptors.len(): {:?}", descriptors.len());
+
+            let desc_request = descriptors[0];
+            if desc_request.is_write_only() {
+				log::trace!("This is write only");
+                return Err(Error::UnexpectedWriteOnlyDescriptor(0));
+            } else {
+				log::trace!("This is read only");
+			}
+
+            if desc_request.len() as usize != size_of::<VirtioConsoleControl>() {
+				log::trace!("UnexpectedDescriptorSize, len = {:?}", desc_request.len());
+                return Err(Error::UnexpectedDescriptorSize(
+                    size_of::<VirtioConsoleControl>(),
+                    desc_request.len(),
+                ));
+            }
+
+			log::trace!("desc_request.len: {}", desc_request.len());
+
+            let mut request = desc_chain
+                .memory()
+                .read_obj::<VirtioConsoleControl>(desc_request.addr())
+                .map_err(|_| Error::DescriptorReadFailed)?;
+
+			self.print_console_frame(request);
+
+			self.handle_control_msg(rx_ctrl_vring, request);
+
+			if let Some(event_fd) = rx_ctrl_vring.get_ref().get_kick() {
+				self.rx_ctrl_event.write(1).unwrap();
+			} else {
+			    // Handle the case where `state` is `None`.
+			    log::trace!("EventFd is not available.");
+			}
+
+            if vring.add_used(desc_chain.head_index(), desc_request.len()).is_err() {
+                log::trace!("Couldn't return used descriptors to the ring");
+                warn!("Couldn't return used descriptors to the ring");
+            }
+        }
+
+        Ok(true)
+    }
+
+    /// Process the messages in the vring and dispatch replies
+    fn process_rx_queue(&mut self, vring: &VringRwLock) -> Result<()> {
+		log::trace!("process_rx_queue");
+        let requests: Vec<_> = vring
+            .get_mut()
+            .get_queue_mut()
+            .iter(self.mem.as_ref().unwrap().memory())
+            .map_err(|_| Error::DescriptorNotFound)?
+            .collect();
+
+        if self.process_rx_requests(requests, vring)? {
+            // Send notification once all the requests are processed
+			log::trace!("Send notification once all the requests of queue 0 are processed");
+            vring
+                .signal_used_queue()
+                .map_err(|_| {
+					log::trace!("NotificationFailed");
+					Error::NotificationFailed
+				})?;
+        }
+		Ok(())
+    }
+
+    /// Process the messages in the vring and dispatch replies
+    fn process_tx_queue(&self, vring: &VringRwLock) -> Result<()> {
+		log::trace!("process_tx_queue");
+        let requests: Vec<_> = vring
+            .get_mut()
+            .get_queue_mut()
+            .iter(self.mem.as_ref().unwrap().memory())
+            .map_err(|_| Error::DescriptorNotFound)?
+            .collect();
+
+        if self.process_tx_requests(requests, vring)? {
+            // Send notification once all the requests are processed
+			log::trace!("Send notification once all the requests of queue 1 are processed");
+            vring
+                .signal_used_queue()
+                .map_err(|_| {
+					log::trace!("signal_used_queue error");
+					Error::NotificationFailed
+				})?;
+        }
+
+        Ok(())
+    }
+
+    /// Process the messages in the vring and dispatch replies
+    fn process_ctrl_rx_queue(&mut self, vring: &VringRwLock) -> Result<()> {
+		log::trace!("process_ctrl_rx_queue");
+        let requests: Vec<_> = vring
+            .get_mut()
+            .get_queue_mut()
+            .iter(self.mem.as_ref().unwrap().memory())
+            .map_err(|_| Error::DescriptorNotFound)?
+            .collect();
+
+        if self.process_ctrl_rx_requests(requests, vring)? {
+			log::trace!("Send notification once all the requests of queue 2 are processed");
+            // Send notification once all the requests are processed
+            vring
+                .signal_used_queue()
+                .map_err(|_| Error::NotificationFailed)?;
+        }
+		Ok(())
+    }
+
+    /// Process the messages in the vring and dispatch replies
+    fn process_ctrl_tx_queue(&mut self, vring: &VringRwLock, rx_ctrl_vring: &VringRwLock) -> Result<()> {
+		log::trace!("process_ctrl_tx_queue");
+        let requests: Vec<_> = vring
+            .get_mut()
+            .get_queue_mut()
+            .iter(self.mem.as_ref().unwrap().memory())
+            .map_err(|_| Error::DescriptorNotFound)?
+            .collect();
+
+        if self.process_ctrl_tx_requests(requests, vring, rx_ctrl_vring)? {
+            // Send notification once all the requests are processed
+            vring
+                .signal_used_queue()
+                .map_err(|_| Error::NotificationFailed)?;
+        }
+		Ok(())
+    }
+
+    /// Set self's VringWorker.
+    pub(crate) fn set_vring_worker(
+		&self,
+        vring_worker: &Arc<VringEpollHandler<Arc<RwLock<VhostUserConsoleBackend>>, VringRwLock, ()>>,
+    ) {
+		let rx_event_fd = self.rx_event.as_raw_fd();
+		vring_worker
+            .register_listener(
+				rx_event_fd,
+				EventSet::IN,
+				u64::from(BACKEND_EFD))
+            .unwrap();
+
+		let rx_ctrl_event_fd = self.rx_ctrl_event.as_raw_fd();
+		vring_worker
+            .register_listener(
+				rx_ctrl_event_fd,
+				EventSet::IN,
+				u64::from(BACKEND_RX_EFD))
+            .unwrap();
+    }
+
+    /// Start console thread.
+    pub(crate) fn start_console_thread(
+		vhu_console: &Arc<RwLock<VhostUserConsoleBackend>>,
+    ) {
+
+		let vhu_console = Arc::clone(&vhu_console);
+    	print!("Enter text and press Enter: ");
+
+		// Spawn a new thread to handle input.
+    	spawn( move || {
+			loop {
+                let ready = vhu_console.read().unwrap().ready_to_write;
+                if ready {
+
+                    let term = Term::stdout();
+                    let character = term.read_char().unwrap();
+				    log::trace!("You entered: {}", character);
+
+                    // Pass the data to vhu_console and trigger an EventFd
+				    vhu_console.write().unwrap().output_buffer = character.to_string();
+            	    vhu_console.write().unwrap().rx_event.write(1).unwrap();
+                }
+			}
+    	});
+    }
+}
+
+/// VhostUserBackendMut trait methods
+impl VhostUserBackendMut<VringRwLock, ()>
+    for VhostUserConsoleBackend
+{
+    fn num_queues(&self) -> usize {
+		log::trace!("num_queues: {:?}", NUM_QUEUES);
+        NUM_QUEUES
+    }
+
+    fn max_queue_size(&self) -> usize {
+		log::trace!("max_queue_size: {:?}", QUEUE_SIZE);
+        QUEUE_SIZE
+    }
+
+    fn features(&self) -> u64 {
+        // this matches the current libvhost defaults except VHOST_F_LOG_ALL
+        let features = 1 << VIRTIO_F_VERSION_1
+            | 1 << VIRTIO_F_NOTIFY_ON_EMPTY
+            | 1 << VIRTIO_RING_F_EVENT_IDX
+			| 1 << VIRTIO_CONSOLE_F_EMERG_WRITE
+            | 1 << VIRTIO_RING_F_INDIRECT_DESC
+			| 1 << VIRTIO_CONSOLE_F_MULTIPORT // This could be disabled
+            | VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits();
+
+		log::trace!("vhu_can->features: {:x}", features);
+		features
+    }
+
+	fn acked_features(&mut self, _features: u64) {
+		log::trace!("\nacked_features: 0x{:x}\n", _features);
+		self.acked_features = _features;
+	}
+
+    fn protocol_features(&self) -> VhostUserProtocolFeatures {
+        let protocol_features = VhostUserProtocolFeatures::MQ
+            | VhostUserProtocolFeatures::CONFIG
+            | VhostUserProtocolFeatures::REPLY_ACK;
+
+		log::trace!("protocol_features: {:x}", protocol_features);
+		protocol_features
+    }
+
+    fn get_config(&self, offset: u32, size: u32) -> Vec<u8> {
+        // SAFETY: The layout of the structure is fixed and can be initialized by
+        // reading its content from byte array.
+		log::trace!("vhu_can->get_config");
+        unsafe {
+            from_raw_parts(
+                self.controller.write().unwrap()
+                    .config()
+                    .as_slice()
+                    .as_ptr()
+                    .offset(offset as isize) as *const _ as *const _,
+                size as usize,
+            )
+            .to_vec()
+        }
+    }
+
+    fn set_event_idx(&mut self, enabled: bool) {
+        dbg!(self.event_idx = enabled);
+    }
+
+    fn update_memory(&mut self, mem: GuestMemoryAtomic<GuestMemoryMmap>) -> IoResult<()> {
+		log::trace!("update_memory\n");
+        self.mem = Some(mem);
+        Ok(())
+    }
+
+    fn handle_event(
+        &mut self,
+        device_event: u16,
+        evset: EventSet,
+        vrings: &[VringRwLock],
+        _thread_id: usize,
+    ) -> IoResult<bool> {
+		log::trace!("\nhandle_event:");
+
+		if device_event == RX_QUEUE {
+		    log::trace!("RX_QUEUE\n");
+		    return Ok(false);
+		};
+
+		if device_event == CTRL_RX_QUEUE {
+		    log::trace!("CTRL_RX_QUEUE\n");
+			if !self.ready {
+				return Ok(false);
+			}
+		};
+
+		let vring = if device_event == BACKEND_EFD {
+		    log::trace!("BACKEND_EFD\n");
+		    &vrings[RX_QUEUE as usize]
+		} else if device_event == BACKEND_RX_EFD {
+		    log::trace!("BACKEND_RX_EFD\n");
+		    &vrings[CTRL_RX_QUEUE as usize]
+		} else {
+			&vrings[device_event as usize]
+		};
+
+        if self.event_idx {
+            // vm-virtio's Queue implementation only checks avail_index
+            // once, so to properly support EVENT_IDX we need to keep
+            // calling process_request_queue() until it stops finding
+            // new requests on the queue.
+            loop {
+                vring.disable_notification().unwrap();
+                match device_event {
+                    TX_QUEUE => {
+				        self.ready_to_write = true;
+                        self.process_tx_queue(vring)
+                    },
+                    CTRL_RX_QUEUE => self.process_ctrl_rx_queue(vring),
+					CTRL_TX_QUEUE => {
+						let rx_ctrl_vring = &vrings[CTRL_RX_QUEUE as usize];
+						self.process_ctrl_tx_queue(vring, rx_ctrl_vring)
+					},
+                    BACKEND_EFD => {
+						let _ = self.rx_event.read();
+						self.process_rx_queue(vring)
+					},
+                    BACKEND_RX_EFD => {
+						let _ = self.rx_ctrl_event.read();
+						self.process_ctrl_rx_queue(vring)
+					},
+                    _ => Err(Error::HandleEventUnknown.into()),
+                }?;
+                if !vring.enable_notification().unwrap() {
+                    break;
+                }
+            }
+        } else {                                                                           
+            // Without EVENT_IDX, a single call is enough.                                 
+            match device_event {
+                TX_QUEUE => {
+			        self.ready_to_write = true;
+                    self.process_tx_queue(vring)
+                },
+                CTRL_RX_QUEUE => self.process_ctrl_rx_queue(vring),
+				CTRL_TX_QUEUE => {
+					let rx_ctrl_vring = &vrings[CTRL_RX_QUEUE as usize];
+					self.process_ctrl_tx_queue(vring, rx_ctrl_vring)
+				},
+                BACKEND_EFD => {
+					let _ = self.rx_event.read();
+					self.process_rx_queue(vring)
+				},
+                BACKEND_RX_EFD => {
+					let _ = self.rx_ctrl_event.read();
+					self.process_ctrl_rx_queue(vring)
+				},
+                _ => Err(Error::HandleEventUnknown.into()),
+            }?;
+        }
+        Ok(false)
+    }
+
+    fn exit_event(&self, _thread_index: usize) -> Option<EventFd> {
+		dbg!("exit_event\n");
+        self.exit_event.try_clone().ok()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_virtio_console_control_byte_valued() {
+        let control = VirtioConsoleControl {
+            id: Le32::from(1),
+            event: Le16::from(2),
+            value: Le16::from(3),
+        };
+
+        let bytes = control.to_le_bytes();
+
+        assert_eq!(bytes.len(), 10);
+    }
+
+    #[test]
+    fn test_vhost_user_console_backend_creation() {
+        let console_controller = Arc::new(RwLock::new(ConsoleController::new(String::from("test_console")).unwrap()));
+        let vhost_user_console_backend = VhostUserConsoleBackend::new(console_controller).unwrap();
+
+        assert_eq!(vhost_user_console_backend.acked_features, 0);
+        assert_eq!(vhost_user_console_backend.event_idx, false);
+        assert_eq!(vhost_user_console_backend.ready, false);
+        assert_eq!(vhost_user_console_backend.ready_to_write, false);
+        assert_eq!(vhost_user_console_backend.output_buffer, String::new());
+    }
+}