[Qemu-devel] [PATCH v6 20/47] Add migration-capability boolean for postcopy-ram.

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

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

The 'postcopy ram' capability allows postcopy migration of RAM;
note that the migration starts off in precopy mode until
postcopy mode is triggered (see the migrate_start_postcopy
patch later in the series).

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 include/migration/migration.h | 1 +
 migration/migration.c         | 9 +++++++++
 qapi-schema.json              | 7 ++++++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index ae85958..5858788 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -179,6 +179,7 @@ void migrate_add_blocker(Error *reason);
  */
 void migrate_del_blocker(Error *reason);
 
+bool migrate_postcopy_ram(void);
 bool migrate_zero_blocks(void);
 
 bool migrate_auto_converge(void);
diff --git a/migration/migration.c b/migration/migration.c
index 01ed1d0..f641fc7 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -685,6 +685,15 @@ void qmp_migrate_set_downtime(double value, Error **errp)
     max_downtime = (uint64_t)value;
 }
 
+bool migrate_postcopy_ram(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->enabled_capabilities[MIGRATION_CAPABILITY_X_POSTCOPY_RAM];
+}
+
 bool migrate_auto_converge(void)
 {
     MigrationState *s;
diff --git a/qapi-schema.json b/qapi-schema.json
index ac9594d..dcd3e62 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -518,10 +518,15 @@
 # @auto-converge: If enabled, QEMU will automatically throttle down the guest
 #          to speed up convergence of RAM migration. (since 1.6)
 #
+# @x-postcopy-ram: Start executing on the migration target before all of RAM has
+#          been migrated, pulling the remaining pages along as needed. NOTE: If
+#          the migration fails during postcopy the VM will fail.  (since 2.4)
+#
 # Since: 1.2
 ##
 { 'enum': 'MigrationCapability',
-  'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks'] }
+  'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
+           'x-postcopy-ram'] }
 
 ##
 # @MigrationCapabilityStatus
-- 
2.1.0