vmstate: Create optional sections To make sections optional, we need to do it at the beggining of the code. Signed-off-by: Juan Quintela <quintela@redhat.com> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 0695d7c..f51ff69 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h

@@ -820,6 +820,8 @@
 void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
                         void *opaque, QJSON *vmdesc);
 
+bool vmstate_save_needed(const VMStateDescription *vmsd, void *opaque);
+
 int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
                                    const VMStateDescription *vmsd,
                                    void *base, int alias_id,

diff --git a/migration/savevm.c b/migration/savevm.c
index 1a9b00b..e779c96 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c

@@ -836,6 +836,11 @@
         if ((!se->ops || !se->ops->save_state) && !se->vmsd) {
             continue;
         }
+        if (se->vmsd && !vmstate_save_needed(se->vmsd, se->opaque)) {
+            trace_savevm_section_skip(se->idstr, se->section_id);
+            continue;
+        }
+
         trace_savevm_section_start(se->idstr, se->section_id);
 
         json_start_object(vmdesc, NULL);
@@ -949,6 +954,9 @@
         if ((!se->ops || !se->ops->save_state) && !se->vmsd) {
             continue;
         }
+        if (se->vmsd && !vmstate_save_needed(se->vmsd, se->opaque)) {
+            continue;
+        }
 
         save_section_header(f, se, QEMU_VM_SECTION_FULL);
 

diff --git a/migration/vmstate.c b/migration/vmstate.c
index 6138d1a..e8ccf22 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c

@@ -276,6 +276,17 @@
     json_end_object(vmdesc);
 }
 
+
+bool vmstate_save_needed(const VMStateDescription *vmsd, void *opaque)
+{
+    if (vmsd->needed && !vmsd->needed(opaque)) {
+        /* optional section not needed */
+        return false;
+    }
+    return true;
+}
+
+
 void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
                         void *opaque, QJSON *vmdesc)
 {

diff --git a/trace-events b/trace-events
index c0111d0..2d395c5 100644
--- a/trace-events
+++ b/trace-events

@@ -1191,6 +1191,7 @@
 qemu_loadvm_state_section_startfull(uint32_t section_id, const char *idstr, uint32_t instance_id, uint32_t version_id) "%u(%s) %u %u"
 savevm_section_start(const char *id, unsigned int section_id) "%s, section_id %u"
 savevm_section_end(const char *id, unsigned int section_id, int ret) "%s, section_id %u -> %d"
+savevm_section_skip(const char *id, unsigned int section_id) "%s, section_id %u"
 savevm_state_begin(void) ""
 savevm_state_header(void) ""
 savevm_state_iterate(void) ""