serial: Add support for NewFileHandleSerialPortAttachment

This makes it possible to have an interactive serial console.

doc/usage.md

@@ -150,9 +150,11 @@ The `--device virtio-net` option adds a network interface to the virtual machine
 #### Description
 
 The `--device virtio-serial` option adds a serial device to the virtual machine. This is useful to redirect text output from the virtual machine to a log file.
+The `logFilePath` and `stdio` arguments are mutually exclusive.
 
 #### Arguments
 - `logFilePath`: path where the serial port output should be written.
+- `stdio`: uses stdin/stdout for the serial console input/output.
 
 #### Example
 `--device virtio-serial,logFilePath=/Users/virtuser/vfkit.log`

pkg/config/virtio.go

@@ -56,7 +56,8 @@ type VirtioNet struct {
 
 // VirtioSerial configures the virtual machine serial ports.
 type VirtioSerial struct {
-	LogFile string
+	LogFile   string
+	UsesStdio bool
 }
 
 // TODO: Add VirtioBalloon
@@ -134,10 +135,31 @@ func VirtioSerialNew(logFilePath string) (VirtioDevice, error) {
 	}, nil
 }
 
+func VirtioSerialNewStdio() (VirtioDevice, error) {
+	return &VirtioSerial{
+		UsesStdio: true,
+	}, nil
+}
+
+func (dev *VirtioSerial) validate() error {
+	if dev.LogFile != "" && dev.UsesStdio {
+		return fmt.Errorf("'logFilePath' and 'stdio' cannot be set at the same time")
+	}
+	if dev.LogFile == "" && !dev.UsesStdio {
+		return fmt.Errorf("One of 'logFilePath' or 'stdio' must be set")
+	}
+
+	return nil
+}
+
 func (dev *VirtioSerial) ToCmdLine() ([]string, error) {
-	if dev.LogFile == "" {
-		return nil, fmt.Errorf("virtio-serial needs the path to the log file")
+	if err := dev.validate(); err != nil {
+		return nil, err
+	}
+	if dev.UsesStdio {
+		return []string{"--device", "virtio-serial,stdio"}, nil
 	}
+
 	return []string{"--device", fmt.Sprintf("virtio-serial,logFilePath=%s", dev.LogFile)}, nil
 }
 
@@ -146,11 +168,17 @@ func (dev *VirtioSerial) FromOptions(options []option) error {
 		switch option.key {
 		case "logFilePath":
 			dev.LogFile = option.value
+		case "stdio":
+			if option.value != "" {
+				return fmt.Errorf("Unexpected value for virtio-serial 'stdio' option: %s", option.value)
+			}
+			dev.UsesStdio = true
 		default:
 			return fmt.Errorf("Unknown option for virtio-serial devices: %s", option.key)
 		}
 	}
-	return nil
+
+	return dev.validate()
 }
 
 // VirtioNetNew creates a new network device for the virtual machine. It will

pkg/config/virtio_test.go

@@ -91,6 +91,13 @@ var virtioDevTests = map[string]virtioDevTest{
 		},
 		expectedCmdLine: []string{"--device", "virtio-serial,logFilePath=/foo/bar.log"},
 	},
+	"NewVirtioSerialStdio": {
+		newDev: func() (VirtioDevice, error) { return VirtioSerialNewStdio() },
+		expectedDev: &VirtioSerial{
+                        UsesStdio: true,
+		},
+		expectedCmdLine: []string{"--device", "virtio-serial,stdio"},
+	},
 	"NewVirtioNet": {
 		newDev: func() (VirtioDevice, error) { return VirtioNetNew("") },
 		expectedDev: &VirtioNet{

pkg/vf/virtio.go

@@ -3,12 +3,15 @@ package vf
 import (
 	"fmt"
 	"net"
+	"os"
 	"path/filepath"
+        "syscall"
 
 	"github.com/crc-org/vfkit/pkg/config"
 
 	"github.com/Code-Hex/vz/v3"
 	log "github.com/sirupsen/logrus"
+        "golang.org/x/sys/unix"
 )
 
 type VirtioBlk config.VirtioBlk
@@ -155,17 +158,46 @@ func (dev *VirtioRng) AddToVirtualMachineConfig(vmConfig *vzVirtualMachineConfig
 	return nil
 }
 
+// https://developer.apple.com/documentation/virtualization/running_linux_in_a_virtual_machine?language=objc#:~:text=Configure%20the%20Serial%20Port%20Device%20for%20Standard%20In%20and%20Out
+func setRawMode(f *os.File) {
+	// Get settings for terminal
+	attr, _ := unix.IoctlGetTermios(int(f.Fd()), unix.TIOCGETA)
+
+	// Put stdin into raw mode, disabling local echo, input canonicalization,
+	// and CR-NL mapping.
+	attr.Iflag &^= syscall.ICRNL
+	attr.Lflag &^= syscall.ICANON | syscall.ECHO
+
+	// Set minimum characters when reading = 1 char
+	attr.Cc[syscall.VMIN] = 1
+
+	// set timeout when reading as non-canonical mode
+	attr.Cc[syscall.VTIME] = 0
+
+	// reflects the changed settings
+	unix.IoctlSetTermios(int(f.Fd()), unix.TIOCSETA, attr)
+}
+
 func (dev *VirtioSerial) AddToVirtualMachineConfig(vmConfig *vzVirtualMachineConfiguration) error {
-	if dev.LogFile == "" {
-		return fmt.Errorf("missing mandatory 'logFile' option for virtio-serial device")
+	if dev.LogFile != "" {
+		log.Infof("Adding virtio-serial device (logFile: %s)", dev.LogFile)
+	}
+	if dev.UsesStdio {
+		log.Infof("Adding stdio console")
 	}
-	log.Infof("Adding virtio-serial device (logFile: %s)", dev.LogFile)
 
-	//serialPortAttachment := vz.NewFileHandleSerialPortAttachment(os.Stdin, tty)
-	serialPortAttachment, err := vz.NewFileSerialPortAttachment(dev.LogFile, false)
+	var serialPortAttachment vz.SerialPortAttachment
+	var err error
+	if dev.UsesStdio {
+		setRawMode(os.Stdin)
+		serialPortAttachment, err = vz.NewFileHandleSerialPortAttachment(os.Stdin, os.Stdout)
+	} else {
+		serialPortAttachment, err = vz.NewFileSerialPortAttachment(dev.LogFile, false)
+	}
 	if err != nil {
 		return err
 	}
+
 	consoleConfig, err := vz.NewVirtioConsoleDeviceSerialPortConfiguration(serialPortAttachment)
 	if err != nil {
 		return err