[PULL 12/41] migration/colo: Use ram_block_discard_disable()

["Michael S. Tsirkin" <mst@redhat.com>]

From: David Hildenbrand <david@redhat.com>

COLO will copy all memory in a RAM block, disable discarding of RAM.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Tested-by: Lukas Straub <lukasstraub2@web.de>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Hailiang Zhang <zhang.zhanghailiang@huawei.com>
Cc: Juan Quintela <quintela@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20200626072248.78761-10-david@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 include/migration/colo.h |  2 +-
 migration/migration.c    |  8 +++++++-
 migration/savevm.c       | 11 +++++++++--
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/migration/colo.h b/include/migration/colo.h
index 1636e6f907..768e1f04c3 100644
--- a/include/migration/colo.h
+++ b/include/migration/colo.h
@@ -25,7 +25,7 @@ void migrate_start_colo_process(MigrationState *s);
 bool migration_in_colo_state(void);
 
 /* loadvm */
-void migration_incoming_enable_colo(void);
+int migration_incoming_enable_colo(void);
 void migration_incoming_disable_colo(void);
 bool migration_incoming_colo_enabled(void);
 void *colo_process_incoming_thread(void *opaque);
diff --git a/migration/migration.c b/migration/migration.c
index d365d82209..92e44e021e 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -338,12 +338,18 @@ bool migration_incoming_colo_enabled(void)
 
 void migration_incoming_disable_colo(void)
 {
+    ram_block_discard_disable(false);
     migration_colo_enabled = false;
 }
 
-void migration_incoming_enable_colo(void)
+int migration_incoming_enable_colo(void)
 {
+    if (ram_block_discard_disable(true)) {
+        error_report("COLO: cannot disable RAM discard");
+        return -EBUSY;
+    }
     migration_colo_enabled = true;
+    return 0;
 }
 
 void migrate_add_address(SocketAddress *address)
diff --git a/migration/savevm.c b/migration/savevm.c
index b979ea6e7f..6e01724605 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2111,8 +2111,15 @@ static int loadvm_handle_recv_bitmap(MigrationIncomingState *mis,
 
 static int loadvm_process_enable_colo(MigrationIncomingState *mis)
 {
-    migration_incoming_enable_colo();
-    return colo_init_ram_cache();
+    int ret = migration_incoming_enable_colo();
+
+    if (!ret) {
+        ret = colo_init_ram_cache();
+        if (ret) {
+            migration_incoming_disable_colo();
+        }
+    }
+    return ret;
 }
 
 /*
-- 
MST