qemu: add pvpanic device to get GUEST_PANICKED event

Listening to the events channel from QEMU and a guest
panic event issued, then we can get the event and do some
work for the special event.

Fixes: #152

Signed-off-by: bin liu <bin@hyper.sh>

qemu/qemu.go

@@ -1118,6 +1118,24 @@ func (blkdev BlockDevice) deviceName(config *Config) string {
 	return string(blkdev.Driver)
 }
 
+// PVPanicDevice represents a qemu pvpanic device.
+type PVPanicDevice struct {
+	NoShutdown bool
+}
+
+// Valid always returns true for pvpanic device
+func (dev PVPanicDevice) Valid() bool {
+	return true
+}
+
+// QemuParams returns the qemu parameters built out of this serial device.
+func (dev PVPanicDevice) QemuParams(config *Config) []string {
+	if dev.NoShutdown {
+		return []string{"-device", "pvpanic", "-no-shutdown"}
+	}
+	return []string{"-device", "pvpanic"}
+}
+
 // VhostUserDevice represents a qemu vhost-user device meant to be passed
 // in to the guest
 type VhostUserDevice struct {

qemu/qemu_test.go

@@ -1203,3 +1203,18 @@ func TestAppendFwcfg(t *testing.T) {
 	}
 	testAppend(fwcfg, fwcfgString, t)
 }
+
+func TestAppendPVPanicDevice(t *testing.T) {
+	testCases := []struct {
+		dev Device
+		out string
+	}{
+		{nil, ""},
+		{PVPanicDevice{}, "-device pvpanic"},
+		{PVPanicDevice{NoShutdown: true}, "-device pvpanic -no-shutdown"},
+	}
+
+	for _, tc := range testCases {
+		testAppend(tc.dev, tc.out, t)
+	}
+}