Add support for s390x on coreos ignition

now x86 platform use fw_cfg to process coreos ingition
but fw_cfg is not usable in s390 platform.

so we need use libguestfs to update the coreos image by
injecting the ignition into it.

we have some comments like following to try but that's not for coreos
https://gitlab.gnome.org/GNOME/gnome-boxes/blob/master/src/unattended-file.vala

Author: jichenjc

libvirt/domain.go

@@ -1,11 +1,16 @@
 package libvirt
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
+	"io"
 	"log"
 	"net"
 	"net/url"
+	"os"
+	"os/exec"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -230,7 +235,143 @@ func newDiskForCloudInit(virConn *libvirt.Connect, volumeKey string) (libvirtxml
 	return disk, nil
 }
 
-func setCoreOSIgnition(d *schema.ResourceData, domainDef *libvirtxml.Domain) error {
+func getFirstDiskPath(d *schema.ResourceData, domainDef *libvirtxml.Domain, virConn *libvirt.Connect) (string, error) {
+	prefix := fmt.Sprintf("disk.%d", 0)
+
+	if volumeKey, ok := d.GetOk(prefix + ".volume_id"); ok {
+		diskVolume, err := virConn.LookupStorageVolByKey(volumeKey.(string))
+		if err != nil {
+			return "", fmt.Errorf("Error lookup storage disk volume: %s", err)
+		}
+		diskVolumeFile, err := diskVolume.GetPath()
+		if err != nil {
+			return "", fmt.Errorf("Error get path of disk volume: %s", err)
+		}
+		return diskVolumeFile, nil
+	}
+	return "", fmt.Errorf("failed to find disk 0")
+}
+
+func getStderr(stderr io.ReadCloser) string {
+	buf := new(bytes.Buffer)
+	buf.ReadFrom(stderr)
+	return buf.String()
+}
+
+func inlineUpdateCoreOsIgnition(d *schema.ResourceData, domainDef *libvirtxml.Domain, virConn *libvirt.Connect) error {
+	if ignition, ok := d.GetOk("coreos_ignition"); ok {
+
+		// Get the root disk (first disk) volume location
+		rootPath, err := getFirstDiskPath(d, domainDef, virConn)
+		if err != nil {
+			return err
+		}
+
+		// Get the ingition file to be uploaded
+		ignitionKey, err := getIgnitionVolumeKeyFromTerraformID(ignition.(string))
+		if err != nil {
+			return err
+		}
+		diskVolume, err := virConn.LookupStorageVolByKey(ignitionKey)
+		if err != nil {
+			return err
+		}
+		fileToUpload, err := diskVolume.GetPath()
+		if err != nil {
+			return err
+		}
+		err = guestfishExecution(rootPath, fileToUpload)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+var execCommand = exec.Command
+
+func guestfishExecution(rootPath string, fileToUpload string) error {
+	// This is the file in coreos image going to be copied from local
+	fileRemoteLocation := "/ignition/config.ign"
+
+	// eval  $(guestfish --listen -a $1)
+	cmd := execCommand("guestfish", "--listen", "-a", rootPath)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return fmt.Errorf("Get stdout failed: %v", err)
+	}
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		return fmt.Errorf("Get stderr failed: %v", err)
+	}
+
+	err = cmd.Start()
+	if err != nil {
+		return fmt.Errorf("Start command failed: %v", err)
+	}
+
+	// if the command start successfully, the output will be following format
+	// GUESTFISH_PID=xxxx; export GUESTFISH_PID, so we need get the PID and set by using os.Setenv
+	buf := new(bytes.Buffer)
+	buf.ReadFrom(stdout)
+	guestfishPidLabel := strings.Split(buf.String(), ";")
+	guestfishPidValue := strings.Split(guestfishPidLabel[0], "=")
+	os.Setenv(guestfishPidValue[0], guestfishPidValue[1])
+
+	// guestfish --remote -- run
+	cmd = execCommand("guestfish", "--remote", "--", "run")
+	err = cmd.Run()
+	if err != nil {
+		return fmt.Errorf("Launch failed: %v, %s", err, getStderr(stderr))
+	}
+
+	// guestfish --remote -- exit
+	defer func() {
+		cmd := execCommand("guestfish", "--remote", "--", "exit")
+		cmd.Run()
+	}()
+
+	// guestfish --remote -- findfs-label
+	cmd = execCommand("guestfish", "--remote", "--", "findfs-label", "boot")
+	output, err := cmd.Output()
+
+	if err != nil {
+		return fmt.Errorf("Failed to find fs label: %v", err)
+	}
+
+	bootDisk := strings.TrimSpace(string(output))
+	if len(bootDisk) == 0 {
+		return fmt.Errorf("failed to get the boot filesystem")
+	}
+
+	// guestfish --remote -- mount $2 /
+	cmd = execCommand("guestfish", "--remote", "--", "mount", bootDisk, "/")
+	err = cmd.Run()
+	if err != nil {
+		return fmt.Errorf("Mount failed: %v, %s", err, getStderr(stderr))
+	}
+
+	// This is the real command that upload the file from current location (the local file system)
+	// to remote file location (the coreos file system)
+	// guestfish --remote -- upload $4 $3/$4
+	cmd = execCommand("guestfish", "--remote", "--", "upload", fileToUpload, fileRemoteLocation)
+	err = cmd.Run()
+	if err != nil {
+		return fmt.Errorf("Upload failed: %v, %s", err, getStderr(stderr))
+	}
+
+	// guestfish --remote -- umount-all
+	cmd = execCommand("guestfish", "--remote", "--", "umount-all")
+	err = cmd.Run()
+	if err != nil {
+		return fmt.Errorf("Unmount failed: %v, %s", err, getStderr(stderr))
+	}
+
+	return nil
+}
+
+// Use fw_cfg device to update coresos
+func fwcfgUpdateCoreOSIgnition(d *schema.ResourceData, domainDef *libvirtxml.Domain) error {
 	if ignition, ok := d.GetOk("coreos_ignition"); ok {
 		ignitionKey, err := getIgnitionVolumeKeyFromTerraformID(ignition.(string))
 		if err != nil {
@@ -252,6 +393,15 @@ func setCoreOSIgnition(d *schema.ResourceData, domainDef *libvirtxml.Domain) err
 	return nil
 }
 
+func updateCoreOSIgnition(d *schema.ResourceData, domainDef *libvirtxml.Domain, virConn *libvirt.Connect) error {
+	if runtime.GOARCH == "s390x" || runtime.GOARCH == "s390" {
+		// There is no support for fw_cfg in s390x, so instead of doing fw_cfg
+		// we have to inline update the coreos ignition file
+		return inlineUpdateCoreOsIgnition(d, domainDef, virConn)
+	}
+	return fwcfgUpdateCoreOSIgnition(d, domainDef)
+}
+
 func setVideo(d *schema.ResourceData, domainDef *libvirtxml.Domain) error {
 	prefix := "video.0"
 	if _, ok := d.GetOk(prefix); ok {