[Qemu-devel] [PATCH v5 25/45] qemu_savevm_state_complete: Postcopy changes

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

When postcopy calls qemu_savevm_state_complete it's not really
the end of migration, so skip:
   a) Finishing postcopiable iterative devices - they'll carry on
   b) The termination byte on the end of the stream.

We then also add:
  qemu_savevm_state_postcopy_complete
which is called at the end of a postcopy migration to call the
complete methods on devices skipped in the _complete call.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 include/sysemu/sysemu.h |  1 +
 savevm.c                | 61 ++++++++++++++++++++++++++++++++++++++++++++-----
 trace-events            |  1 +
 3 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 5f518b3..0f2e4ed 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -114,6 +114,7 @@ void qemu_savevm_state_cancel(void);
 void qemu_savevm_state_pending(QEMUFile *f, uint64_t max_size,
                                uint64_t *res_non_postcopiable,
                                uint64_t *res_postcopiable);
+void qemu_savevm_state_postcopy_complete(QEMUFile *f);
 void qemu_savevm_command_send(QEMUFile *f, enum qemu_vm_cmd command,
                               uint16_t len, uint8_t *data);
 void qemu_savevm_send_ping(QEMUFile *f, uint32_t value);
diff --git a/savevm.c b/savevm.c
index 2ea4c76..1e8d289 100644
--- a/savevm.c
+++ b/savevm.c
@@ -865,12 +865,54 @@ int qemu_savevm_state_iterate(QEMUFile *f)
     return ret;
 }
 
+/*
+ * Calls the complete routines just for those devices that are postcopiable;
+ * causing the last few pages to be sent immediately and doing any associated
+ * cleanup.
+ * Note postcopy also calls the plain qemu_savevm_state_complete to complete
+ * all the other devices, but that happens at the point we switch to postcopy.
+ */
+void qemu_savevm_state_postcopy_complete(QEMUFile *f)
+{
+    SaveStateEntry *se;
+    int ret;
+
+    QTAILQ_FOREACH(se, &savevm_handlers, entry) {
+        if (!se->ops || !se->ops->save_live_complete ||
+            !(se->ops->can_postcopy &&
+              se->ops->can_postcopy(se->opaque))) {
+            continue;
+        }
+        if (se->ops && se->ops->is_active) {
+            if (!se->ops->is_active(se->opaque)) {
+                continue;
+            }
+        }
+        trace_savevm_section_start(se->idstr, se->section_id);
+        /* Section type */
+        qemu_put_byte(f, QEMU_VM_SECTION_END);
+        qemu_put_be32(f, se->section_id);
+
+        ret = se->ops->save_live_complete(f, se->opaque);
+        trace_savevm_section_end(se->idstr, se->section_id, ret);
+        if (ret < 0) {
+            qemu_file_set_error(f, ret);
+            return;
+        }
+    }
+
+    qemu_savevm_send_postcopy_end(f, 0 /* Good */);
+    qemu_put_byte(f, QEMU_VM_EOF);
+    qemu_fflush(f);
+}
+
 void qemu_savevm_state_complete(QEMUFile *f)
 {
     QJSON *vmdesc;
     int vmdesc_len;
     SaveStateEntry *se;
     int ret;
+    bool in_postcopy = migration_postcopy_phase(migrate_get_current());
 
     trace_savevm_state_complete();
 
@@ -885,6 +927,11 @@ void qemu_savevm_state_complete(QEMUFile *f)
                 continue;
             }
         }
+        if (in_postcopy && se->ops &&  se->ops->can_postcopy &&
+            se->ops->can_postcopy(se->opaque)) {
+            trace_qemu_savevm_state_complete_skip_for_postcopy(se->idstr);
+            continue;
+        }
         trace_savevm_section_start(se->idstr, se->section_id);
         /* Section type */
         qemu_put_byte(f, QEMU_VM_SECTION_END);
@@ -931,15 +978,17 @@ void qemu_savevm_state_complete(QEMUFile *f)
         trace_savevm_section_end(se->idstr, se->section_id, 0);
     }
 
-    qemu_put_byte(f, QEMU_VM_EOF);
-
     json_end_array(vmdesc);
     qjson_finish(vmdesc);
-    vmdesc_len = strlen(qjson_get_str(vmdesc));
+    if (!in_postcopy) {
+        /* Postcopy stream will still be going */
+        qemu_put_byte(f, QEMU_VM_EOF);
+        vmdesc_len = strlen(qjson_get_str(vmdesc));
 
-    qemu_put_byte(f, QEMU_VM_VMDESCRIPTION);
-    qemu_put_be32(f, vmdesc_len);
-    qemu_put_buffer(f, (uint8_t *)qjson_get_str(vmdesc), vmdesc_len);
+        qemu_put_byte(f, QEMU_VM_VMDESCRIPTION);
+        qemu_put_be32(f, vmdesc_len);
+        qemu_put_buffer(f, (uint8_t *)qjson_get_str(vmdesc), vmdesc_len);
+    }
     object_unref(OBJECT(vmdesc));
 
     qemu_fflush(f);
diff --git a/trace-events b/trace-events
index 941976a..a555b56 100644
--- a/trace-events
+++ b/trace-events
@@ -1185,6 +1185,7 @@ loadvm_process_command(uint16_t com, uint16_t len) "com=0x%x len=%d"
 loadvm_process_command_ping(uint32_t val) "%x"
 qemu_savevm_send_postcopy_advise(void) ""
 qemu_savevm_send_postcopy_ram_discard(void) ""
+qemu_savevm_state_complete_skip_for_postcopy(const char *section) "skipping: %s"
 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_send_ping(uint32_t val) "%x"
-- 
2.1.0