1 files changed, 53 insertions, 26 deletions

diff --git a/migration/migration.c b/migration/migration.c
index 915c8cc11f..74099b361f 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -588,43 +588,49 @@ MigrationInfo *qmp_query_migrate(Error **errp)
     return info;
 }
 
-void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
-                                  Error **errp)
+/**
+ * @migration_caps_check - check capability validity
+ *
+ * @cap_list: old capability list, array of bool
+ * @params: new capabilities to be applied soon
+ * @errp: set *errp if the check failed, with reason
+ *
+ * Returns true if check passed, otherwise false.
+ */
+static bool migrate_caps_check(bool *cap_list,
+                               MigrationCapabilityStatusList *params,
+                               Error **errp)
 {
-    MigrationState *s = migrate_get_current();
     MigrationCapabilityStatusList *cap;
-    bool old_postcopy_cap = migrate_postcopy_ram();
+    bool old_postcopy_cap;
 
-    if (migration_is_setup_or_active(s->state)) {
-        error_setg(errp, QERR_MIGRATION_ACTIVE);
-        return;
-    }
+    old_postcopy_cap = cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM];
 
     for (cap = params; cap; cap = cap->next) {
+        cap_list[cap->value->capability] = cap->value->state;
+    }
+
 #ifndef CONFIG_LIVE_BLOCK_MIGRATION
-        if (cap->value->capability == MIGRATION_CAPABILITY_BLOCK
-            && cap->value->state) {
-            error_setg(errp, "QEMU compiled without old-style (blk/-b, inc/-i) "
-                       "block migration");
-            error_append_hint(errp, "Use drive_mirror+NBD instead.\n");
-            continue;
-        }
-#endif
-        s->enabled_capabilities[cap->value->capability] = cap->value->state;
+    if (cap_list[MIGRATION_CAPABILITY_BLOCK]) {
+        error_setg(errp, "QEMU compiled without old-style (blk/-b, inc/-i) "
+                   "block migration");
+        error_append_hint(errp, "Use drive_mirror+NBD instead.\n");
+        return false;
     }
+#endif
 
-    if (migrate_postcopy_ram()) {
-        if (migrate_use_compression()) {
+    if (cap_list[MIGRATION_CAPABILITY_POSTCOPY_RAM]) {
+        if (cap_list[MIGRATION_CAPABILITY_COMPRESS]) {
             /* The decompression threads asynchronously write into RAM
              * rather than use the atomic copies needed to avoid
              * userfaulting.  It should be possible to fix the decompression
              * threads for compatibility in future.
              */
-            error_report("Postcopy is not currently compatible with "
-                         "compression");
-            s->enabled_capabilities[MIGRATION_CAPABILITY_POSTCOPY_RAM] =
-                false;
+            error_setg(errp, "Postcopy is not currently compatible "
+                       "with compression");
+            return false;
         }
+
         /* This check is reasonably expensive, so only when it's being
          * set the first time, also it's only the destination that needs
          * special support.
@@ -634,11 +640,32 @@ void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
             /* postcopy_ram_supported_by_host will have emitted a more
              * detailed message
              */
-            error_report("Postcopy is not supported");
-            s->enabled_capabilities[MIGRATION_CAPABILITY_POSTCOPY_RAM] =
-                false;
+            error_setg(errp, "Postcopy is not supported");
+            return false;
         }
     }
+
+    return true;
+}
+
+void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
+                                  Error **errp)
+{
+    MigrationState *s = migrate_get_current();
+    MigrationCapabilityStatusList *cap;
+
+    if (migration_is_setup_or_active(s->state)) {
+        error_setg(errp, QERR_MIGRATION_ACTIVE);
+        return;
+    }
+
+    if (!migrate_caps_check(s->enabled_capabilities, params, errp)) {
+        return;
+    }
+
+    for (cap = params; cap; cap = cap->next) {
+        s->enabled_capabilities[cap->value->capability] = cap->value->state;
+    }
 }
 
 /*