[RFC PATCH v2 18/20] hw/core/qdev: Display warning for devices missing migration state

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

When built with --enable-qdev-debug, QEMU displays warnings
listing devices missing migration state:

  $ qemu-system-arm -S -M spitz
  qemu-system-arm: warning: missing migration state for type: 'pxa270-c0-arm-cpu'
  qemu-system-arm: warning: missing migration state for type: 'serial'
  qemu-system-arm: warning: missing migration state for type: 'pxa2xx-pcmcia'
  qemu-system-arm: warning: missing migration state for type: 'pxa2xx-pcmcia'
  qemu-system-arm: warning: missing migration state for type: 'pxa2xx-i2c-slave'
  qemu-system-arm: warning: missing migration state for type: 'pxa2xx-i2c-slave'
  qemu-system-arm: warning: missing migration state for type: 'ads7846'
  qemu-system-arm: warning: missing migration state for type: 'max1111'

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
Unresolved issue:

https://www.mail-archive.com/qemu-devel@nongnu.org/msg721700.html
Peter:
> I think where we'd like to get to is installing a migration
> blocker if the machine has any devices which don't have a vmsd.
> But for that we'd need to be pretty sure we'd got all the devices
> on machines where we care about migration, and we're clearly a
> fair way from that (eg we need to do something about the
> devices like the CPU which don't have a vmsd but handle their
> migration some other way so they don't trigger the condition
> for warning/migration-blocker).
---
 configure      | 10 ++++++++++
 meson.build    |  1 +
 hw/core/qdev.c |  5 +++++
 3 files changed, 16 insertions(+)

diff --git a/configure b/configure
index 155dda124c2..984befbb99d 100755
--- a/configure
+++ b/configure
@@ -383,6 +383,7 @@ blobs="true"
 pkgversion=""
 pie=""
 qom_cast_debug="yes"
+qdev_debug="no"
 trace_backends="log"
 trace_file="trace"
 spice="$default_feature"
@@ -1005,6 +1006,10 @@ for opt do
   ;;
   --enable-qom-cast-debug) qom_cast_debug="yes"
   ;;
+  --disable-qdev-debug) qdev_debug="no"
+  ;;
+  --enable-qdev-debug) qdev_debug="yes"
+  ;;
   --disable-virtfs) virtfs="disabled"
   ;;
   --enable-virtfs) virtfs="enabled"
@@ -1048,6 +1053,7 @@ for opt do
       debug="yes"
       strip_opt="no"
       fortify_source="no"
+      qdev_debug="yes"
   ;;
   --enable-sanitizers) sanitizers="yes"
   ;;
@@ -5912,6 +5918,10 @@ if test "$qom_cast_debug" = "yes" ; then
   echo "CONFIG_QOM_CAST_DEBUG=y" >> $config_host_mak
 fi
 
+if test "$qdev_debug" = "yes" ; then
+  echo "CONFIG_QDEV_DEBUG=y" >> $config_host_mak
+fi
+
 echo "CONFIG_COROUTINE_BACKEND=$coroutine" >> $config_host_mak
 if test "$coroutine_pool" = "yes" ; then
   echo "CONFIG_COROUTINE_POOL=1" >> $config_host_mak
diff --git a/meson.build b/meson.build
index 3d889857a09..545c8f9f88b 100644
--- a/meson.build
+++ b/meson.build
@@ -2472,6 +2472,7 @@
 summary_info += {'TPM support':       config_host.has_key('CONFIG_TPM')}
 summary_info += {'libssh support':    config_host.has_key('CONFIG_LIBSSH')}
 summary_info += {'QOM debugging':     config_host.has_key('CONFIG_QOM_CAST_DEBUG')}
+summary_info += {'QDEV debugging':    config_host.has_key('CONFIG_QDEV_DEBUG')}
 summary_info += {'Live block migration': config_host.has_key('CONFIG_LIVE_BLOCK_MIGRATION')}
 summary_info += {'lzo support':       lzo.found()}
 summary_info += {'snappy support':    snappy.found()}
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index f0d0afd438d..9a73a242fa4 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -792,6 +792,11 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
                                                &local_err) < 0) {
                 goto post_realize_fail;
             }
+        } else {
+#ifdef CONFIG_QDEV_DEBUG
+            warn_report("missing migration state for type: '%s'",
+                        object_get_typename(OBJECT(dev)));
+#endif
         }
 
         /*
-- 
2.26.2