qemu: Support monitoring for failures in the initramfs

Pairs with coreos/ignition-dracut#146

What we really want is to use this in kola, will do as a
separate followup.

mantle/cmd/kola/qemuexec.go

@@ -52,7 +52,8 @@ var (
 
 	ignitionFragments []string
 
-	forceConfigInjection bool
+	forceConfigInjection      bool
+	propagateInitramfsFailure bool
 )
 
 func init() {
@@ -65,6 +66,8 @@ func init() {
 	cmdQemuExec.Flags().IntVarP(&memory, "memory", "m", 0, "Memory in MB")
 	cmdQemuExec.Flags().StringVarP(&ignition, "ignition", "i", "", "Path to ignition config")
 	cmdQemuExec.Flags().BoolVarP(&forceConfigInjection, "inject-ignition", "", false, "Force injecting Ignition config using guestfs")
+	cmdQemuExec.Flags().BoolVar(&propagateInitramfsFailure, "propagate-initramfs-failure", false, "Error out if the system fails in the initramfs")
+
 }
 
 func renderFragments() (string, error) {
@@ -187,8 +190,13 @@ func runQemuExec(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	// Ignore errors
-	_ = inst.Wait()
-
-	return nil
+	if propagateInitramfsFailure {
+		err = inst.WaitAll()
+		if err != nil {
+			return err
+		}
+		return nil
+	} else {
+		return inst.Wait()
+	}
 }

mantle/platform/qemu.go

@@ -15,6 +15,7 @@
 package platform
 
 import (
+	"bufio"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -47,6 +48,8 @@ type QemuInstance struct {
 	qemu      exec.Cmd
 	swtpmTmpd string
 	swtpm     exec.Cmd
+
+	JournalPipe os.File
 }
 
 func (inst *QemuInstance) Pid() int {
@@ -111,10 +114,57 @@ func (inst *QemuInstance) SSHAddress() (string, error) {
 	return "", fmt.Errorf("didn't find an address")
 }
 
+// Wait for the qemu process to exit
 func (inst *QemuInstance) Wait() error {
 	return inst.qemu.Wait()
 }
 
+// WaitIgnitionError will only return if the instance
+// failed inside the initramfs.  The resulting string will
+// be a newline-delimited stream of JSON strings, as returned
+// by `journalctl -o json`.
+func (inst *QemuInstance) WaitIgnitionError() (string, error) {
+	b := bufio.NewReaderSize(&inst.JournalPipe, 64768)
+	var r strings.Builder
+	iscorrupted := false
+	for {
+		line, prefix, err := b.ReadLine()
+		if err != nil {
+			return r.String(), errors.Wrapf(err, "Reading from journal channel")
+		}
+		if prefix {
+			iscorrupted = true
+		}
+		if string(line) == "{}" {
+			break
+		}
+		r.Write(line)
+	}
+	if iscorrupted {
+		return r.String(), fmt.Errorf("journal was truncated due to overly long line")
+	}
+	return r.String(), nil
+}
+
+// WaitAll wraps the process exit as well as WaitIgnitionError,
+// returning an error if either fail.
+func (inst *QemuInstance) WaitAll() error {
+	c := make(chan error)
+	go func() {
+		_, err := inst.WaitIgnitionError()
+		// TODO parse buf and try to nicely render something
+		if err != nil {
+			c <- err
+		} else {
+			c <- fmt.Errorf("instance failed in the initramfs")
+		}
+	}()
+	go func() {
+		c <- inst.Wait()
+	}()
+	return <-c
+}
+
 func (inst *QemuInstance) Destroy() {
 	if inst.qemu != nil {
 		if err := inst.qemu.Kill(); err != nil {
@@ -689,6 +739,17 @@ func (builder *QemuBuilder) Exec() (*QemuInstance, error) {
 			"-tpmdev", "emulator,id=tpm0,chardev=chrtpm", "-device", "tpm-tis,tpmdev=tpm0")
 	}
 
+	// Set up the virtio channel to get Ignition failures by default
+	journalPipeR, journalPipeW, err := os.Pipe()
+	if err != nil {
+		return nil, errors.Wrapf(err, "creating journal pipe")
+	}
+	inst.JournalPipe = *journalPipeR
+	argv = append(argv, "-device", "virtio-serial")
+	// https://www.redhat.com/archives/libvir-list/2015-December/msg00305.html
+	argv = append(argv, "-chardev", fmt.Sprintf("file,id=ignition-dracut,path=%s,append=on", builder.AddFd(journalPipeW)))
+	argv = append(argv, "-device", "virtserialport,chardev=ignition-dracut,name=com.coreos.ignition.journal")
+
 	fdnum := 3 // first additional file starts at position 3
 	for i, _ := range builder.fds {
 		fdset := i + 1 // Start at 1