configure: Support enable/disable COLO feature

configure --enable-colo/--disable-colo to switch COLO
support on/off.

COLO feature doesn't depend on any other external libraries,
So here it is reasonable to enable COLO by default, to
avoid re-compile QEMU if users want to use this capability.

Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Amit Shah <amit@amitshah.net>

configure

@@ -230,6 +230,7 @@ vhost_net="no"
 vhost_scsi="no"
 vhost_vsock="no"
 kvm="no"
+colo="yes"
 rdma=""
 gprof="no"
 debug_tcg="no"
@@ -918,6 +919,10 @@ for opt do
   ;;
   --enable-kvm) kvm="yes"
   ;;
+  --disable-colo) colo="no"
+  ;;
+  --enable-colo) colo="yes"
+  ;;
   --disable-tcg-interpreter) tcg_interpreter="no"
   ;;
   --enable-tcg-interpreter) tcg_interpreter="yes"
@@ -1366,6 +1371,7 @@ disabled with --disable-FEATURE, default is enabled if available:
   fdt             fdt device tree
   bluez           bluez stack connectivity
   kvm             KVM acceleration support
+  colo            COarse-grain LOck-stepping VM for Non-stop Service
   rdma            RDMA-based migration support
   vde             support for vde network
   netmap          support for netmap network
@@ -5004,6 +5010,7 @@ echo "Linux AIO support $linux_aio"
 echo "ATTR/XATTR support $attr"
 echo "Install blobs     $blobs"
 echo "KVM support       $kvm"
+echo "COLO support      $colo"
 echo "RDMA support      $rdma"
 echo "TCG interpreter   $tcg_interpreter"
 echo "fdt support       $fdt"
@@ -5639,6 +5646,10 @@ if have_backend "syslog"; then
 fi
 echo "CONFIG_TRACE_FILE=$trace_file" >> $config_host_mak
 
+if test "$colo" = "yes"; then
+  echo "CONFIG_COLO=y" >> $config_host_mak
+fi
+
 if test "$rdma" = "yes" ; then
   echo "CONFIG_RDMA=y" >> $config_host_mak
 fi

migration/colo.c

@@ -24,7 +24,7 @@
 
 bool colo_supported(void)
 {
-    return false;
+    return true;
 }
 
 bool migration_in_colo_state(void)