Update vhost-device-console

Simplify the code, include Epilys's comments.
The device was tested with:
1) Upstream QEMU's vhost-user-device

    qemu-system-x86_64  \
            -m 4096 \
            -numa node,memdev=mem \
            -object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
            -chardev socket,id=char1,path=/tmp/console.sock \
            -device vhost-user-device-pci,chardev=char1,virtio-id=3,num_vqs=4,config_size=12 \
            ...

2) A new QEMU vhost-user-console device which can be found in the following repo:
- https://github.com/virtualopensystems/qemu/tree/vhu-console-rfc

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>

staging/Cargo.toml

@@ -1,6 +1,6 @@
 [workspace]
 resolver = "2"
 members = [
-  "vhost-device-video",
   "vhost-device-console",
+  "vhost-device-video",
 ]

staging/vhost-device-console/Cargo.toml

@@ -19,17 +19,20 @@ console = "0.15.7"
 queues = "1.0.2"
 clap = { version = "4.4",  features = ["derive"] }
 env_logger = "0.10"
+epoll = "4.3"
 libc = "0.2"
 log = "0.4"
+rand = "0.8.5"
+tempfile = "3.9"
 thiserror = "1.0"
-vhost = { version = "0.8", features = ["vhost-user-slave"] }
-vhost-user-backend = "0.10"
-virtio-bindings = "0.2.1"
-virtio-queue = "0.9"
-vm-memory = "0.12"
+vhost = { version = "0.9", features = ["vhost-user-backend"] }
+vhost-user-backend = "0.11"
+virtio-bindings = "0.2.2"
+virtio-queue = "0.10"
+vm-memory = "0.13.1"
 vmm-sys-util = "0.11"
 
 [dev-dependencies]
 assert_matches = "1.5"
-virtio-queue = { version = "0.9", features = ["test-utils"] }
-vm-memory = { version = "0.12", features = ["backend-mmap", "backend-atomic"] }
+virtio-queue = { version = "0.10", features = ["test-utils"] }
+vm-memory = { version = "0.13", features = ["backend-mmap", "backend-atomic"] }

staging/vhost-device-console/README.md

@@ -1,9 +1,9 @@
 # vhost-device-console - Console emulation backend daemon
 
-## Description
-This program is a vhost-user backend that emulates a VirtIO Console device.
-
 ## Synopsis
+```text
+vhost-device-can --socket-path=<SOCKET_PATH>
+```
 
 ## Options
 
@@ -15,31 +15,86 @@ This program is a vhost-user backend that emulates a VirtIO Console device.
 
 .. option:: -s, --socket-path=PATH
 
-  Location of vhost-user Unix domain sockets, this path will be suffixed with
-  0,1,2..socket_count-1.
+  Location of vhost-user Unix domain sockets
 
-.. option:: -p, --console-path=PATH
 
-  Location of Unix socket, this socket will be used to forward all the virtio
-  console traffic (not used in the current code version)
+## Description
 
-## Examples
+This program is a vhost-user backend that emulates a VirtIO Console device.
+The device's binary takes as parameter a socket which is commonly used 
+across all vhost-devices to communicate with the vhost-user frontend device.
 
-The daemon should be started first:
+This program is tested with QEMU's `vhost-user-device-pci` device and
+Virtio-loopback's `-device vhost-user-can`.
+Examples' section below.
 
-::
+This program is a vhost-user backend that emulates a VirtIO Console device.
 
-  host# vhost-device-console --socket-path=console.sock
+## Limitations
 
-The virtio-loopback invocation needs to insert the [virtio-loopback-transport](https://git.virtualopensystems.com/virtio-loopback/loopback_driver/-/tree/epsilon-release) driver and then start the [virtio-loopback-adapter](https://git.virtualopensystems.com/virtio-loopback/adapter_app/-/tree/epsilon-release) which is the intermediate between vhost-device and virtio-loopback-transport driver.
+This device is still work-in-progress (WIP). Currently the device works
+only with one guest at the time (no multi-guest support).
 
-For more information please check the virtio-loopback [guide](https://git.virtualopensystems.com/virtio-loopback/docs/-/tree/epsilon-release) and the [design document](https://git.virtualopensystems.com/virtio-loopback/docs/-/blob/epsilon-release/design_docs/EG-VIRT_VOSYS_virtio_loopback_design_v1.4_2023_04_03.pdf).
+## Next steps
 
-::
+Next development steps are:
+1) Enable multi-guest support
+2) Update the restart process of the device
 
-  host# sudo insmod loopback_driver.ko
-  host# sudo ./adapter -s /path/to/console.sock0 -d vhuconsole
+## Features
 
+The current device gives access to a QEMU guest by providing a login prompt.
+This prompt appears as soon as the guest is fully booted and gives the ability
+to user run command as a in regular terminal.
+
+## Examples
+
+### Dependencies
+For testing the device the required dependencies are:
+- Linux:
+    - Set `CONFIG_VIRTIO_CONSOLE=y`
+- QEMU (optional):
+    - A new vhost-user-console device has been implemented in the following repo:
+      - https://github.com/virtualopensystems/qemu/tree/vhu-console-rfc
+
+
+### Test the device
+
+The daemon should be started first:
+```shell
+host# vhost-device-can --socket-path=can.sock --can-in="can0" --can-out="can1"
+```
+
+The QEMU invocation needs to create a chardev socket the device can
+use to communicate as well as share the guests memory over a memfd.
+
+There are two option for running QEMU with vhost-device-console:
+
+1) Using `vhost-user-console-pci`:
+```text
+host# qemu-system                                          \
+    -m 4096                                                \
+    -numa node,memdev=mem                                  \
+    -object memory-backend-memfd,id=mem,size=4G,share=on   \
+    -chardev socket,path=/tmp/console.sock,id=con          \
+    -device vhost-user-console-pci,chardev=con0,id=console \
+    ...
+```
+
+> Note: For testing this scenario the reader needs to clone the QEMU version from the following repo
+>       which implements `vhost-user-console` device.
+> - https://github.com/virtualopensystems/qemu/tree/vhu-console-rfc
+
+2) Using `vhost-user-device-pci`:
+```text
+host# qemu-system                                                                   \
+    -m 4096                                                                         \
+    -numa node,memdev=mem                                                           \
+    -object memory-backend-memfd,id=mem,size=4G,share=on                            \
+    -chardev socket,id=con0,path=/tmp/console.sock                                  \
+    -device vhost-user-device-pci,chardev=con0,virtio-id=3,num_vqs=4,config_size=12 \
+    ...
+```
 
 ## License