feat : add writer implementation

src/main.rs

@@ -24,7 +24,7 @@ struct VMMOpts {
 
     /// Stdout console file path
     #[clap(long)]
-    console: Option<String>
+    console: Option<String>,
 }
 
 #[derive(Debug)]
@@ -47,8 +47,22 @@ fn main() -> Result<(), Error> {
     // * Memory size (in MB)
     // * Path to a Linux kernel
     // * Optional path to console file
-    vmm.configure(opts.cpus, opts.memory, &opts.kernel, opts.console)
-        .map_err(Error::VmmConfigure)?;
+    vmm.configure(
+        opts.cpus,
+        opts.memory,
+        &opts.kernel,
+        opts.console,
+        Option::None,
+    )
+    .map_err(Error::VmmConfigure)?;
+
+    // To use Writer with serial device :
+    // * Create mpsc channel :
+    // let (tx, rx) = std::sync::mpsc::channel();
+    // * Create a new Writer
+    // let writer = Writer::new(tx);
+    // * Add the Writer when configuring the VMM
+    // * Use the rx receiver to read the data
 
     // Run the VMM
     vmm.run().map_err(Error::VmmRun)?;

src/vmm/src/devices/mod.rs

@@ -1,3 +1,30 @@
 // SPDX-License-Identifier: Apache-2.0
 
+use std::io::{Result, Write};
+use std::sync::mpsc;
+
 pub(crate) mod serial;
+
+pub struct Writer {
+    tx: mpsc::Sender<String>,
+}
+
+impl Write for Writer {
+    fn write(&mut self, buf: &[u8]) -> Result<usize> {
+        let s = String::from_utf8_lossy(buf);
+        self.tx
+            .send(s.to_string())
+            .map_err(|_| std::io::Error::new(std::io::ErrorKind::Other, "Error sending data"))?;
+        Ok(buf.len())
+    }
+
+    fn flush(&mut self) -> Result<()> {
+        Ok(())
+    }
+}
+
+impl Writer {
+    pub fn new(tx: mpsc::Sender<String>) -> Self {
+        Writer { tx }
+    }
+}

src/vmm/src/lib.rs

@@ -8,14 +8,15 @@ extern crate linux_loader;
 extern crate vm_memory;
 extern crate vm_superio;
 
+use std::fs::File;
 use std::io::stdout;
 use std::os::unix::io::AsRawFd;
 use std::os::unix::prelude::RawFd;
 use std::sync::{Arc, Mutex};
 use std::thread;
 use std::{io, path::PathBuf};
-use std::fs::File;
 
+use devices::Writer;
 use kvm_bindings::{kvm_userspace_memory_region, KVM_MAX_CPUID_ENTRIES};
 use kvm_ioctls::{Kvm, VmFd};
 use linux_loader::loader::{self, KernelLoaderResult};
@@ -66,6 +67,8 @@ pub enum Error {
     TerminalConfigure(kvm_ioctls::Error),
     /// Console configuration error
     ConsoleError(io::Error),
+    /// Writer configuration error
+    WriterError(io::Error),
 }
 
 /// Dedicated [`Result`](https://doc.rust-lang.org/std/result/) type.
@@ -164,10 +167,15 @@ impl VMM {
         Ok(())
     }
 
-    pub fn configure_console(
-        &mut self,
-        console_path: Option<String>
-    ) -> Result<()> {
+    pub fn configure_writer(&mut self, writer: Option<Writer>) -> Result<()> {
+        if let Some(writer) = writer {
+            let mut serial = self.serial.lock().unwrap();
+            *serial = LumperSerial::new(Box::new(writer)).map_err(Error::WriterError)?;
+        }
+        Ok(())
+    }
+
+    pub fn configure_console(&mut self, console_path: Option<String>) -> Result<()> {
         if let Some(console_path) = console_path {
             // We create the file if it does not exist, else we open
             let file = File::create(&console_path).map_err(Error::ConsoleError)?;
@@ -266,8 +274,16 @@ impl VMM {
         }
     }
 
-    pub fn configure(&mut self, num_vcpus: u8, mem_size_mb: u32, kernel_path: &str, console: Option<String>) -> Result<()> {
+    pub fn configure(
+        &mut self,
+        num_vcpus: u8,
+        mem_size_mb: u32,
+        kernel_path: &str,
+        console: Option<String>,
+        writer: Option<Writer>,
+    ) -> Result<()> {
         self.configure_console(console)?;
+        self.configure_writer(writer);
         self.configure_memory(mem_size_mb)?;
         let kernel_load = kernel::kernel_setup(&self.guest_memory, PathBuf::from(kernel_path))?;
         self.configure_io()?;