vmm: replace eprintln with log::error

Unify log formatting and printing as `eprintln!` and `log::error!`
would be used alongside each other.
When using e.g. `env_logger` lines printed with `eprintln!` would
lack formatting / colors.
Currently only relevant in `ch-remote` + `cli_print_error_chain`.

Note that the replaced messages now also end up in the logfile of
`cloud-hypervisor` when configured and not any longer in stderr.

Signed-off-by: Maximilian Güntner <code@mguentner.de>

src/lib.rs

@@ -4,6 +4,8 @@
 
 use std::error::Error;
 
+use log::error;
+
 /// Prints a chain of errors to the user in a consistent manner.
 /// The user will see a clear chain of errors, followed by debug output
 /// for opening issues.
@@ -19,10 +21,10 @@ pub fn cli_print_error_chain<'a>(
 ) {
     eprint!("Error: {component} exited with the following ");
     if top_error.source().is_none() {
-        eprintln!("error:");
-        eprintln!("  {top_error}");
+        error!("error:");
+        error!("  {top_error}");
     } else {
-        eprintln!("chain of errors:");
+        error!("chain of errors:");
         std::iter::successors(Some(top_error), |sub_error| {
             // Dereference necessary to mitigate rustc compiler bug.
             // See <https://github.com/rust-lang/rust/issues/141673>
@@ -32,13 +34,13 @@ pub fn cli_print_error_chain<'a>(
         .for_each(|(level, error)| {
             // Special case: handling of HTTP Server responses in ch-remote
             if let Some(message) = display_modifier(level, 2, error) {
-                eprintln!("{message}");
+                error!("{message}");
             } else {
-                eprintln!("  {level}: {error}");
+                error!("  {level}: {error}");
             }
         });
     }
 
-    eprintln!();
-    eprintln!("Debug Info: {top_error:?}");
+    error!("");
+    error!("Debug Info: {top_error:?}");
 }

src/main.rs

@@ -15,7 +15,7 @@ use std::{env, io};
 use clap::{Arg, ArgAction, ArgGroup, ArgMatches, Command};
 use event_monitor::event;
 use libc::EFD_NONBLOCK;
-use log::{warn, LevelFilter};
+use log::{error, warn, LevelFilter};
 use option_parser::OptionParser;
 use seccompiler::SeccompAction;
 use signal_hook::consts::SIGSYS;
@@ -561,7 +561,7 @@ fn start_vmm(cmd_arguments: ArgMatches) -> Result<Option<String>, Error> {
                 signal_hook::low_level::emulate_default_handler(SIGSYS).unwrap();
             })
         }
-        .map_err(|e| eprintln!("Error adding SIGSYS signal handler: {e}"))
+        .map_err(|e| error!("Error adding SIGSYS signal handler: {e}"))
         .ok();
     }
 
@@ -575,13 +575,13 @@ fn start_vmm(cmd_arguments: ArgMatches) -> Result<Option<String>, Error> {
     // dedicated signal handling thread we'll start in a bit.
     for sig in &vmm::vm::Vm::HANDLED_SIGNALS {
         if let Err(e) = block_signal(*sig) {
-            eprintln!("Error blocking signals: {e}");
+            error!("Error blocking signals: {e}");
         }
     }
 
     for sig in &vmm::Vmm::HANDLED_SIGNALS {
         if let Err(e) = block_signal(*sig) {
-            eprintln!("Error blocking signals: {e}");
+            error!("Error blocking signals: {e}");
         }
     }