[Qemu-devel] [PATCH v5 15/45] Rework loadvm path for subloops

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

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

Postcopy needs to have two migration streams loading concurrently;
one from memory (with the device state) and the other from the fd
with the memory transactions.

Split the core of qemu_loadvm_state out so we can use it for both.

Allow the inner loadvm loop to quit and signal whether the parent
should.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 savevm.c     | 106 ++++++++++++++++++++++++++++++++++++-----------------------
 trace-events |   4 +++
 2 files changed, 69 insertions(+), 41 deletions(-)

diff --git a/savevm.c b/savevm.c
index f42713d..4b619da 100644
--- a/savevm.c
+++ b/savevm.c
@@ -951,6 +951,16 @@ static SaveStateEntry *find_se(const char *idstr, int instance_id)
     return NULL;
 }
 
+/* ORable flags that control the (potentially nested) loadvm_state loops */
+enum LoadVMExitCodes {
+    /* Quit the loop level that received this command */
+    LOADVM_QUIT_LOOP     =  1,
+    /* Quit this loop and our parent */
+    LOADVM_QUIT_PARENT   =  2,
+};
+
+static int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis);
+
 static int loadvm_process_command_simple_lencheck(const char *name,
                                                   unsigned int actual,
                                                   unsigned int expected)
@@ -967,6 +977,8 @@ static int loadvm_process_command_simple_lencheck(const char *name,
 /*
  * Process an incoming 'QEMU_VM_COMMAND'
  * negative return on error (will issue error message)
+ * 0   just a normal return
+ * 1   All good, but exit the loop
  */
 static int loadvm_process_command(QEMUFile *f)
 {
@@ -1036,36 +1048,13 @@ void loadvm_free_handlers(MigrationIncomingState *mis)
     }
 }
 
-int qemu_loadvm_state(QEMUFile *f)
+static int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis)
 {
-    MigrationIncomingState *mis = migration_incoming_get_current();
-    Error *local_err = NULL;
     uint8_t section_type;
-    unsigned int v;
     int ret;
+    int exitcode = 0;
 
-    if (qemu_savevm_state_blocked(&local_err)) {
-        error_report("%s", error_get_pretty(local_err));
-        error_free(local_err);
-        return -EINVAL;
-    }
-
-    v = qemu_get_be32(f);
-    if (v != QEMU_VM_FILE_MAGIC) {
-        error_report("Not a migration stream");
-        return -EINVAL;
-    }
-
-    v = qemu_get_be32(f);
-    if (v == QEMU_VM_FILE_VERSION_COMPAT) {
-        error_report("SaveVM v2 format is obsolete and don't work anymore");
-        return -ENOTSUP;
-    }
-    if (v != QEMU_VM_FILE_VERSION) {
-        error_report("Unsupported migration stream version");
-        return -ENOTSUP;
-    }
-
+    trace_qemu_loadvm_state_main();
     while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
         uint32_t instance_id, version_id, section_id;
         SaveStateEntry *se;
@@ -1093,16 +1082,14 @@ int qemu_loadvm_state(QEMUFile *f)
             if (se == NULL) {
                 error_report("Unknown savevm section or instance '%s' %d",
                              idstr, instance_id);
-                ret = -EINVAL;
-                goto out;
+                return -EINVAL;
             }
 
             /* Validate version */
             if (version_id > se->version_id) {
                 error_report("savevm: unsupported version %d for '%s' v%d",
                              version_id, idstr, se->version_id);
-                ret = -EINVAL;
-                goto out;
+                return -EINVAL;
             }
 
             /* Add entry */
@@ -1117,7 +1104,7 @@ int qemu_loadvm_state(QEMUFile *f)
             if (ret < 0) {
                 error_report("error while loading state for instance 0x%x of"
                              " device '%s'", instance_id, idstr);
-                goto out;
+                return ret;
             }
             break;
         case QEMU_VM_SECTION_PART:
@@ -1132,36 +1119,73 @@ int qemu_loadvm_state(QEMUFile *f)
             }
             if (le == NULL) {
                 error_report("Unknown savevm section %d", section_id);
-                ret = -EINVAL;
-                goto out;
+                return -EINVAL;
             }
 
             ret = vmstate_load(f, le->se, le->version_id);
             if (ret < 0) {
                 error_report("error while loading state section id %d(%s)",
                              section_id, le->se->idstr);
-                goto out;
+                return ret;
             }
             break;
         case QEMU_VM_COMMAND:
             ret = loadvm_process_command(f);
-            if (ret < 0) {
-                goto out;
+            trace_qemu_loadvm_state_section_command(ret);
+            if ((ret < 0) || (ret & LOADVM_QUIT_LOOP)) {
+                return ret;
             }
+            exitcode |= ret; /* Lets us pass flags up to the parent */
             break;
         default:
             error_report("Unknown savevm section type %d", section_type);
-            ret = -EINVAL;
-            goto out;
+            return -EINVAL;
         }
     }
 
-    cpu_synchronize_all_post_init();
+    if (exitcode & LOADVM_QUIT_PARENT) {
+        trace_qemu_loadvm_state_main_quit_parent();
+        exitcode &= ~LOADVM_QUIT_PARENT;
+        exitcode |= LOADVM_QUIT_LOOP;
+    }
+
+    return exitcode;
+}
+
+int qemu_loadvm_state(QEMUFile *f)
+{
+    MigrationIncomingState *mis = migration_incoming_get_current();
+    Error *local_err = NULL;
+    unsigned int v;
+    int ret;
+
+    if (qemu_savevm_state_blocked(&local_err)) {
+        error_report("%s", error_get_pretty(local_err));
+        error_free(local_err);
+        return -EINVAL;
+    }
+
+    v = qemu_get_be32(f);
+    if (v != QEMU_VM_FILE_MAGIC) {
+        error_report("Not a migration stream");
+        return -EINVAL;
+    }
+
+    v = qemu_get_be32(f);
+    if (v == QEMU_VM_FILE_VERSION_COMPAT) {
+        error_report("SaveVM v2 format is obsolete and don't work anymore");
+        return -ENOTSUP;
+    }
+    if (v != QEMU_VM_FILE_VERSION) {
+        error_report("Unsupported migration stream version");
+        return -ENOTSUP;
+    }
 
-    ret = 0;
+    ret = qemu_loadvm_state_main(f, mis);
 
-out:
+    trace_qemu_loadvm_state_post_main(ret);
     if (ret == 0) {
+        cpu_synchronize_all_post_init();
         ret = qemu_file_get_error(f);
     }
 
diff --git a/trace-events b/trace-events
index 1951b25..4ff55fe 100644
--- a/trace-events
+++ b/trace-events
@@ -1165,7 +1165,11 @@ vmware_setmode(uint32_t w, uint32_t h, uint32_t bpp) "%dx%d @ %d bpp"
 
 # savevm.c
 qemu_loadvm_state_section(unsigned int section_type) "%d"
+qemu_loadvm_state_section_command(int ret) "%d"
 qemu_loadvm_state_section_partend(uint32_t section_id) "%u"
+qemu_loadvm_state_main(void) ""
+qemu_loadvm_state_main_quit_parent(void) ""
+qemu_loadvm_state_post_main(int ret) "%d"
 qemu_loadvm_state_section_startfull(uint32_t section_id, const char *idstr, uint32_t instance_id, uint32_t version_id) "%u(%s) %u %u"
 loadvm_process_command(uint16_t com, uint16_t len) "com=0x%x len=%d"
 loadvm_process_command_ping(uint32_t val) "%x"
-- 
2.1.0