[PATCH 3/6] migration: Add no-ram capability

[Nikita Lapshin]

This capability disable RAM section in migration stream.

Signed-off-by: Nikita Lapshin <nikita.lapshin@virtuozzo.com>
---
 migration/migration.c | 9 +++++++++
 migration/migration.h | 1 +
 migration/ram.c       | 6 ++++++
 qapi/migration.json   | 8 +++++---
 4 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 3de11ae921..006447d00a 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2610,6 +2610,15 @@ bool migrate_background_snapshot(void)
     return s->enabled_capabilities[MIGRATION_CAPABILITY_BACKGROUND_SNAPSHOT];
 }
 
+bool migrate_no_ram(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_NO_RAM];
+}
+
 /* migration thread support */
 /*
  * Something bad happened to the RP stream, mark an error
diff --git a/migration/migration.h b/migration/migration.h
index 8130b703eb..43f7bf8eba 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -358,6 +358,7 @@ int migrate_decompress_threads(void);
 bool migrate_use_events(void);
 bool migrate_postcopy_blocktime(void);
 bool migrate_background_snapshot(void);
+bool migrate_no_ram(void);
 
 /* Sending on the return path - generic and then for each message type */
 void migrate_send_rp_shut(MigrationIncomingState *mis,
diff --git a/migration/ram.c b/migration/ram.c
index 57efa67f20..aa3583d0bc 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4339,6 +4339,11 @@ static int ram_resume_prepare(MigrationState *s, void 
*opaque)
     return 0;
 }
 
+static bool ram_is_active(void* opaque)
+{
+    return !migrate_no_ram();
+}
+
 static SaveVMHandlers savevm_ram_handlers = {
     .save_setup = ram_save_setup,
     .save_live_iterate = ram_save_iterate,
@@ -4351,6 +4356,7 @@ static SaveVMHandlers savevm_ram_handlers = {
     .load_setup = ram_load_setup,
     .load_cleanup = ram_load_cleanup,
     .resume_prepare = ram_resume_prepare,
+    .is_active = ram_is_active,
 };
 
 static void ram_mig_ram_block_resized(RAMBlockNotifier *n, void *host,
diff --git a/qapi/migration.json b/qapi/migration.json
index bbfd48cf0b..d53956852c 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -452,6 +452,8 @@
 #                       procedure starts. The VM RAM is saved with running VM.
 #                       (since 6.0)
 #
+# @no-ram: If enabled, migration stream won't contain any ram in it. (since 
7.0)
+#
 # Features:
 # @unstable: Members @x-colo and @x-ignore-shared are experimental.
 #
@@ -465,8 +467,7 @@
            'block', 'return-path', 'pause-before-switchover', 'multifd',
            'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
            { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
-           'validate-uuid', 'background-snapshot'] }
-
+           'validate-uuid', 'background-snapshot', 'no-ram'] }
 ##
 # @MigrationCapabilityStatus:
 #
@@ -519,7 +520,8 @@
 #       {"state": false, "capability": "compress"},
 #       {"state": true, "capability": "events"},
 #       {"state": false, "capability": "postcopy-ram"},
-#       {"state": false, "capability": "x-colo"}
+#       {"state": false, "capability": "x-colo"},
+#       {"state": false, "capability": "no-ram"}
 #    ]}
 #
 ##
-- 
2.27.0