Raw block device passthrough support

cmd/ls.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log/slog"
 	"os"
+	"path/filepath"
 	"strconv"
 	"strings"
 
@@ -35,7 +36,7 @@ var lsCmd = &cobra.Command{
 	},
 }
 
-func getDevicePassthroughConfig(val string) vm.USBDevicePassthroughConfig {
+func getDevicePassthroughConfig(val string) vm.PassthroughConfig {
 	valSplit := strings.Split(val, ":")
 	if want, have := 2, len(valSplit); want != have {
 		slog.Error("Bad device passthrough syntax", "error", fmt.Errorf("wrong items split by ':' count: want %v, have %v", want, have))
@@ -62,14 +63,33 @@ func getDevicePassthroughConfig(val string) vm.USBDevicePassthroughConfig {
 			os.Exit(1)
 		}
 
-		return vm.USBDevicePassthroughConfig{
-			VendorID:  uint16(vendorID),
-			ProductID: uint16(productID),
+		return vm.PassthroughConfig{
+			USB: []vm.USBDevicePassthroughConfig{{
+				VendorID:  uint16(vendorID),
+				ProductID: uint16(productID),
+			}},
 		}
+	case "dev":
+		devPath := filepath.Clean(valSplit[1])
+		stat, err := os.Stat(devPath)
+		if err != nil {
+			slog.Error("Failed to stat the device path", "error", err.Error(), "path", devPath)
+			os.Exit(1)
+		}
+
+		isDev := stat.Mode()&os.ModeDevice != 0
+		if !isDev {
+			slog.Error("Provided path is not a path to a valid block device", "path", devPath, "file-mode", stat.Mode())
+			os.Exit(1)
+		}
+
+		return vm.PassthroughConfig{Block: []vm.BlockDevicePassthroughConfig{{
+			Path: devPath,
+		}}}
 	default:
 		slog.Error("Unknown device passthrough type", "value", valSplit[0])
 		os.Exit(1)
 		// This unreachable code is required to compile.
-		return vm.USBDevicePassthroughConfig{}
+		return vm.PassthroughConfig{}
 	}
 }

cmd/utils.go

@@ -51,10 +51,10 @@ func doUSBRootCheck() {
 }
 
 func runVM(passthroughArg string, fn func(context.Context, *vm.VM, *vm.FileManager) int, forwardPortsRules []vm.PortForwardingRule, unrestrictedNetworking bool) int {
-	var passthroughConfig []vm.USBDevicePassthroughConfig
+	var passthroughConfig vm.PassthroughConfig
 
 	if passthroughArg != "" {
-		passthroughConfig = []vm.USBDevicePassthroughConfig{getDevicePassthroughConfig(passthroughArg)}
+		passthroughConfig = getDevicePassthroughConfig(passthroughArg)
 		doUSBRootCheck()
 	}
 
@@ -66,7 +66,7 @@ func runVM(passthroughArg string, fn func(context.Context, *vm.VM, *vm.FileManag
 
 		MemoryAlloc: vmMemAllocFlag,
 
-		USBDevices:               passthroughConfig,
+		PassthroughConfig:        passthroughConfig,
 		ExtraPortForwardingRules: forwardPortsRules,
 
 		OSUpTimeout:  time.Duration(vmOSUpTimeoutFlag) * time.Second,

vm/os_specifics.go

@@ -4,7 +4,11 @@ package vm
 
 import (
 	"os/exec"
+	"path/filepath"
+	"strings"
 	"syscall"
+
+	"github.com/pkg/errors"
 )
 
 func prepareVMCmd(cmd *exec.Cmd) {
@@ -17,3 +21,26 @@ func prepareVMCmd(cmd *exec.Cmd) {
 func terminateProcess(pid int) error {
 	return syscall.Kill(-pid, syscall.SIGTERM)
 }
+
+// This is never used except for a band-aid that would check
+// that there are no double-mounts.
+func checkDeviceSeemsMounted(devPathPrefix string) (bool, error) {
+	absDevPathPrefix, err := filepath.Abs(devPathPrefix)
+	if err != nil {
+		return false, errors.Wrap(err, "get abs path")
+	}
+
+	mounts, err := exec.Command("mount").Output()
+	if err != nil {
+		return false, errors.Wrap(err, "run mount command")
+	}
+
+	for _, line := range strings.Split(string(mounts), "\n") {
+		// I know, I know, this is a rare band-aid.
+		if strings.HasPrefix(line, devPathPrefix) || strings.HasPrefix(line, absDevPathPrefix) {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}

vm/passthrough.go

@@ -0,0 +1,15 @@
+package vm
+
+type USBDevicePassthroughConfig struct {
+	VendorID  uint16
+	ProductID uint16
+}
+
+type BlockDevicePassthroughConfig struct {
+	Path string
+}
+
+type PassthroughConfig struct {
+	USB   []USBDevicePassthroughConfig
+	Block []BlockDevicePassthroughConfig
+}

vm/ssh.go

@@ -103,10 +103,10 @@ func (vm *VM) sshSetup() (ssh.Signer, error) {
 
 	installSSHDCmd := ""
 	if vm.installSSH {
-		installSSHDCmd = "apk add openssh; "
+		installSSHDCmd = "ifconfig eth0 up && ifconfig lo up && udhcpc; apk add openssh; "
 	}
 
-	cmd := `do_setup () { sh -c "set -ex; setup-alpine -q; ` + installSSHDCmd + `mkdir -p ~/.ssh; echo ` + shellescape.Quote(string(sshPublicKey)) + ` > ~/.ssh/authorized_keys; rc-update add sshd; rc-service sshd start"; echo "SERIAL"" ""STATUS: $?"; }; do_setup` + "\n"
+	cmd := `do_setup () { sh -c "set -ex; ` + installSSHDCmd + `mkdir -p ~/.ssh; echo ` + shellescape.Quote(string(sshPublicKey)) + ` > ~/.ssh/authorized_keys; rc-update add sshd; rc-service sshd start"; echo "SERIAL"" ""STATUS: $?"; }; do_setup` + "\n"
 
 	err = vm.writeSerial([]byte(cmd))
 	if err != nil {

vm/types.go

@@ -9,11 +9,6 @@ import (
 	"github.com/pkg/errors"
 )
 
-type USBDevicePassthroughConfig struct {
-	VendorID  uint16
-	ProductID uint16
-}
-
 type PortForwardingRule struct {
 	HostIP   net.IP
 	HostPort uint16

vm/vm.go

@@ -54,6 +54,8 @@ type VM struct {
 	// These are to be interacted with using `atomic` package
 	disposed uint32
 	canceled uint32
+
+	originalCfg VMConfig
 }
 
 type DriveConfig struct {
@@ -67,7 +69,7 @@ type VMConfig struct {
 
 	MemoryAlloc uint32 // In KiB.
 
-	USBDevices               []USBDevicePassthroughConfig
+	PassthroughConfig        PassthroughConfig
 	ExtraPortForwardingRules []PortForwardingRule
 
 	// Timeouts
@@ -149,26 +151,43 @@ func NewVM(logger *slog.Logger, cfg VMConfig) (*VM, error) {
 		cmdArgs = append(cmdArgs, "-device", "virtio-gpu-device")
 	}
 
-	if len(cfg.USBDevices) != 0 {
-		cmdArgs = append(cmdArgs, "-device", "nec-usb-xhci")
-
-		for _, dev := range cfg.USBDevices {
-			cmdArgs = append(cmdArgs, "-device", "usb-host,vendorid=0x"+hex.EncodeToString(utils.Uint16ToBytesBE(dev.VendorID))+",productid=0x"+hex.EncodeToString(utils.Uint16ToBytesBE(dev.ProductID)))
-		}
-	}
-
 	for i, extraDrive := range cfg.Drives {
 		_, err = os.Stat(extraDrive.Path)
 		if err != nil {
 			return nil, errors.Wrapf(err, "stat extra drive #%v path", i)
 		}
 
-		driveArgs := "file=" + shellescape.Quote(extraDrive.Path) + ",format=qcow2,if=virtio"
+		driveArgs := "file=" + shellescape.Quote(extraDrive.Path) + ",format=qcow2,if=none,id=disk" + fmt.Sprint(i)
 		if extraDrive.SnapshotMode {
 			driveArgs += ",snapshot=on"
 		}
 
-		cmdArgs = append(cmdArgs, "-drive", driveArgs)
+		cmdArgs = append(cmdArgs, "-drive", driveArgs, "-device", "virtio-blk-pci,drive=disk"+fmt.Sprint(i)+",bootindex="+fmt.Sprint(i))
+	}
+
+	if len(cfg.PassthroughConfig.USB) != 0 {
+		cmdArgs = append(cmdArgs, "-device", "nec-usb-xhci")
+
+		for _, dev := range cfg.PassthroughConfig.USB {
+			cmdArgs = append(cmdArgs, "-device", "usb-host,vendorid=0x"+hex.EncodeToString(utils.Uint16ToBytesBE(dev.VendorID))+",productid=0x"+hex.EncodeToString(utils.Uint16ToBytesBE(dev.ProductID)))
+		}
+	}
+
+	for _, dev := range cfg.PassthroughConfig.Block {
+		// It's always a user's responsibility to ensure that no drives are mounted
+		// in both host and guest system. This should serve as the last resort.
+		{
+			seemsMounted, err := checkDeviceSeemsMounted(dev.Path)
+			if err != nil {
+				return nil, errors.Wrapf(err, "check whether device seems to be mounted (path '%v')", dev.Path)
+			}
+
+			if seemsMounted {
+				return nil, fmt.Errorf("device '%v' is already mounted in the host system", dev.Path)
+			}
+		}
+
+		cmdArgs = append(cmdArgs, "-drive", "file="+shellescape.Quote(dev.Path)+",format=raw,aio=native,cache=none")
 	}
 
 	// We're not using clean `cdromImagePath` here because it is set to "."
@@ -235,6 +254,8 @@ func NewVM(logger *slog.Logger, cfg VMConfig) (*VM, error) {
 
 		osUpTimeout:  osUpTimeout,
 		sshUpTimeout: sshUpTimeout,
+
+		originalCfg: cfg,
 	}
 
 	vm.resetSerialStdout()
@@ -252,6 +273,8 @@ func (vm *VM) Run() error {
 		return errors.Wrap(err, "start qemu cmd")
 	}
 
+	go vm.runPeriodicHostMountChecker()
+
 	var globalErrsMu sync.Mutex
 	var globalErrs []error
 
@@ -499,3 +522,30 @@ func (vm *VM) DialSCP() (*scp.Client, error) {
 func (vm *VM) SSHUpNotifyChan() chan struct{} {
 	return vm.sshReadyCh
 }
+
+// It's always a user's responsibility to ensure that no drives are mounted
+// in both host and guest system. This should serve as the last resort.
+func (vm *VM) runPeriodicHostMountChecker() {
+	if len(vm.originalCfg.PassthroughConfig.Block) == 0 {
+		return
+	}
+
+	for {
+		select {
+		case <-vm.ctx.Done():
+			return
+		case <-time.After(time.Second):
+			for _, dev := range vm.originalCfg.PassthroughConfig.Block {
+				seemsMounted, err := checkDeviceSeemsMounted(dev.Path)
+				if err != nil {
+					vm.logger.Warn("Failed to check if a passed device seems to be mounted", "dev-path", dev.Path)
+					continue
+				}
+
+				if seemsMounted {
+					panic(fmt.Sprintf("CRITICAL: Passed-through device '%v' appears to have been mounted on the host OS. Forcefully exiting now to prevent data corruption.", dev.Path))
+				}
+			}
+		}
+	}
+}