qemu: allow specifying the machine type

spread/qemu.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"regexp"
 	"strconv"
 
 	"golang.org/x/net/context"
@@ -121,7 +122,30 @@ func biosPath(biosName string) (string, error) {
 	return "", fmt.Errorf("cannot find bios path for %q", biosName)
 }
 
+func machineType(system *System) (string, error) {
+	// Utilise the variable to determine which QEMU machine type should be
+	// used. Use the "pc" QEMU machine type if nothing is specified.
+	if system.Plan == "" {
+		system.Plan = "pc"
+	}
+
+	// Make sure that the value for the machine type is sane and does not
+	// allow the user to pass arbitrary arguments to QEMU by ensuring that
+	// the value is a single word.
+	r := regexp.MustCompile(`^\S+$`)
+	if !r.Match([]byte(system.Plan)) {
+		return "", fmt.Errorf(`invalid machine type: "%s"`, system.Plan)
+	}
+
+	return system.Plan, nil
+}
+
 func qemuCmd(system *System, path string, mem, port int) (*exec.Cmd, error) {
+	machine, err := machineType(system)
+	if err != nil {
+		return nil, err
+	}
+
 	serial := fmt.Sprintf("telnet:127.0.0.1:%d,server,nowait", port+100)
 	monitor := fmt.Sprintf("telnet:127.0.0.1:%d,server,nowait", port+200)
 	fwd := fmt.Sprintf("user,hostfwd=tcp:127.0.0.1:%d-:22", port)
@@ -133,6 +157,7 @@ func qemuCmd(system *System, path string, mem, port int) (*exec.Cmd, error) {
 		"-net", fwd,
 		"-serial", serial,
 		"-monitor", monitor,
+		"-M", machine,
 		path)
 	if os.Getenv("SPREAD_QEMU_GUI") != "1" {
 		cmd.Args = append([]string{cmd.Args[0], "-nographic"}, cmd.Args[1:]...)

spread/qemu_test.go

@@ -1,6 +1,7 @@
 package spread_test
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -91,3 +92,43 @@ func (s *qemuSuite) TestQemuCmdWithEfi(c *C) {
 		c.Check(strings.Contains(s, ":-bios:/usr/share/OVMF/OVMF_CODE.fd:"), Equals, tc.UseBiosQemuOption)
 	}
 }
+
+func (s *qemuSuite) TestQemuMachineTypes(c *C) {
+	imageName := "ubuntu-20.06-64"
+
+	restore := makeMockQemuImg(c, imageName)
+	defer restore()
+
+	tests := []struct {
+		machineType         string
+		expectedMachineType string
+		expectedErr         string
+	}{
+		// Make sure the default is "pc"
+		{"", "pc", ""},
+		// Make sure the specified machine type is used
+		{"q35", "q35", ""},
+		// Do not allow multiple words
+		{"invalid machine", "", `invalid machine type: "invalid machine"`},
+	}
+
+	for _, tc := range tests {
+		ms := &spread.System{
+			Name:    "some-name",
+			Image:   imageName,
+			Backend: "qemu",
+			Plan:    tc.machineType,
+		}
+		cmd, err := spread.QemuCmd(ms, "/path/to/image", 512, 9999)
+
+		if tc.expectedErr != "" {
+			c.Check(err, ErrorMatches, tc.expectedErr)
+			continue
+		}
+		c.Assert(err, IsNil)
+
+		s := strings.Join(cmd.Args, " ")
+		// Make sure the QEMU command specifies the given machine type, e.g. "-M pc"
+		c.Assert(s, Matches, fmt.Sprintf("^.*-M %s.*$", tc.expectedMachineType))
+	}
+}