[PATCH 4/6] migration: Add ram-only capability

[Nikita Lapshin]

If this capability is enabled migration stream
will have RAM section only.

Signed-off-by: Nikita Lapshin <nikita.lapshin@virtuozzo.com>
---
 migration/migration.c | 20 +++++++++++++++++++-
 migration/migration.h |  1 +
 migration/savevm.c    | 11 ++++++++++-
 qapi/migration.json   |  7 +++++--
 4 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 006447d00a..4d7ef9d8dc 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1257,6 +1257,14 @@ static bool migrate_caps_check(bool *cap_list,
         return false;
     }
 
+    if (cap_list[MIGRATION_CAPABILITY_NO_RAM] &&
+        cap_list[MIGRATION_CAPABILITY_RAM_ONLY]) {
+        error_setg(errp, "ram-only and no-ram aren't "
+                         "compatible with each other");
+
+        return false;
+    }
+
     return true;
 }
 
@@ -2619,6 +2627,15 @@ bool migrate_no_ram(void)
     return s->enabled_capabilities[MIGRATION_CAPABILITY_NO_RAM];
 }
 
+bool migrate_ram_only(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_RAM_ONLY];
+}
+
 /* migration thread support */
 /*
  * Something bad happened to the RP stream, mark an error
@@ -3973,7 +3990,8 @@ static void *bg_migration_thread(void *opaque)
      * save their state to channel-buffer along with devices.
      */
     cpu_synchronize_all_states();
-    if (qemu_savevm_state_complete_precopy_non_iterable(fb, false, false)) {
+    if (!migrate_ram_only() &&
+        qemu_savevm_state_complete_precopy_non_iterable(fb, false, false)) {
         goto fail;
     }
     /*
diff --git a/migration/migration.h b/migration/migration.h
index 43f7bf8eba..d5a077e00d 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -359,6 +359,7 @@ bool migrate_use_events(void);
 bool migrate_postcopy_blocktime(void);
 bool migrate_background_snapshot(void);
 bool migrate_no_ram(void);
+bool migrate_ram_only(void);
 
 /* Sending on the return path - generic and then for each message type */
 void migrate_send_rp_shut(MigrationIncomingState *mis,
diff --git a/migration/savevm.c b/migration/savevm.c
index ba644083ab..e41ca76000 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -249,6 +249,7 @@ typedef struct SaveStateEntry {
     void *opaque;
     CompatEntry *compat;
     int is_iterable;
+    bool is_ram;
 } SaveStateEntry;
 
 typedef struct SaveState {
@@ -802,6 +803,10 @@ int register_savevm_live(const char *idstr,
         se->is_iterable = 1;
     }
 
+    if (!strcmp("ram", idstr)) {
+        se->is_ram = true;
+    }
+
     pstrcat(se->idstr, sizeof(se->idstr), idstr);
 
     if (instance_id == VMSTATE_INSTANCE_ID_ANY) {
@@ -949,6 +954,10 @@ static bool should_skip(SaveStateEntry *se)
         return true;
     }
 
+    if (migrate_ram_only() && !se->is_ram) {
+        return true;
+    }
+
     return false;
 }
 
@@ -1486,7 +1495,7 @@ int qemu_savevm_state_complete_precopy(QEMUFile *f, bool 
iterable_only,
         }
     }
 
-    if (iterable_only) {
+    if (iterable_only || migrate_ram_only()) {
         goto flush;
     }
 
diff --git a/qapi/migration.json b/qapi/migration.json
index d53956852c..626fc59d14 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -454,6 +454,8 @@
 #
 # @no-ram: If enabled, migration stream won't contain any ram in it. (since 
7.0)
 #
+# @ram-only: If enabled, only RAM sections will be sent. (since 7.0)
+#
 # Features:
 # @unstable: Members @x-colo and @x-ignore-shared are experimental.
 #
@@ -467,7 +469,7 @@
            'block', 'return-path', 'pause-before-switchover', 'multifd',
            'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
            { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
-           'validate-uuid', 'background-snapshot', 'no-ram'] }
+           'validate-uuid', 'background-snapshot', 'no-ram', 'ram-only'] }
 ##
 # @MigrationCapabilityStatus:
 #
@@ -521,7 +523,8 @@
 #       {"state": true, "capability": "events"},
 #       {"state": false, "capability": "postcopy-ram"},
 #       {"state": false, "capability": "x-colo"},
-#       {"state": false, "capability": "no-ram"}
+#       {"state": false, "capability": "no-ram"},
+#       {"state": false, "capability": "ram-only"}
 #    ]}
 #
 ##
-- 
2.27.0