Add persist option to vm library.

BUG=
TEST=Tested by persisting, ctrl+c, continuing and using same vm.
Also without --persist

Review URL: http://codereview.chromium.org/3419014

Change-Id: I49e26eb86101e8b8b50e58a9f277d62d5fadc664

bin/cros_run_vm_update

@@ -32,3 +32,4 @@ $(dirname $0)/../image_to_live.sh \
   --ssh_port=${FLAGS_ssh_port} \
   --stateful_update_flag=${stateful_flags} \
   --image=$(readlink -f ${FLAGS_update_image_path})
+

lib/cros_vm_lib.sh

@@ -0,0 +1,73 @@
+# Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+#
+# Common vm functions for use in crosutils.
+
+DEFINE_string kvm_pid "" \
+  "Use this pid file.  If it exists and is set, use the vm specified by pid."
+DEFINE_boolean no_graphics ${FLAGS_FALSE} "Runs the KVM instance silently."
+DEFINE_boolean persist "${FLAGS_FALSE}" "Persist vm."
+DEFINE_boolean snapshot ${FLAGS_FALSE} "Don't commit changes to image."
+DEFINE_integer ssh_port 9222 "Port to tunnel ssh traffic over."
+
+
+KVM_PID_FILE=/tmp/kvm.$$.pid
+
+function get_pid() {
+  sudo cat "${KVM_PID_FILE}"
+}
+
+# TODO(rtc): These flags assume that we'll be using KVM on Lucid and won't work
+# on Hardy.
+# $1: Path to the virtual image to start.
+function start_kvm() {
+  # Override default pid file.
+  [ -n "${FLAGS_kvm_pid}" ] && KVM_PID_FILE=${FLAGS_kvm_pid}
+  if [ -e "${KVM_PID_FILE}" ]; then
+    local pid=$(get_pid)
+    # Check if the process exists.
+    if ps -p ${pid} > /dev/null ; then
+      echo "Using a pre-created KVM instance specified by ${FLAGS_kvm_pid}."
+    else
+      # Let's be safe in case they specified a file that isn't a pid file.
+      echo "File ${KVM_PID_FILE} exists but specified pid doesn't."
+      exit 1
+    fi
+  else
+    # No pid specified by PID file.  Let's create a VM instance in this case.
+    echo "Starting a KVM instance"
+    local nographics=""
+    local usesnapshot=""
+    if [ ${FLAGS_no_graphics} -eq ${FLAGS_TRUE} ]; then
+      nographics="-nographic"
+    fi
+
+    if [ ${FLAGS_snapshot} -eq ${FLAGS_TRUE} ]; then
+      snapshot="-snapshot"
+    fi
+
+    sudo kvm -m 1024 \
+      -vga std \
+      -pidfile "${KVM_PID_FILE}" \
+      -daemonize \
+      -net nic \
+      ${nographics} \
+      ${snapshot} \
+      -net user,hostfwd=tcp::${FLAGS_ssh_port}-:22 \
+      -hda "${1}"
+  fi
+}
+
+function stop_kvm() {
+  if [ "${FLAGS_persist}" -eq "${FLAGS_TRUE}" ]; then
+    echo "Persist requested.  Use --ssh_port ${FLAGS_ssh_port} " \
+      "--kvm_pid ${KVM_PID_FILE} to re-connect to it."
+  else
+    echo "Stopping the KVM instance"
+    local pid=$(get_pid)
+    echo "Killing ${pid}"
+    sudo kill ${pid}
+    sudo rm "${KVM_PID_FILE}"
+  fi
+}