[PATCH v3 01/20] multifd: Add capability to enable/disable zero_page

[Hao Xiang]

From: Juan Quintela <quintela@redhat.com>

We have to enable it by default until we introduce the new code.

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 migration/options.c | 15 +++++++++++++++
 migration/options.h |  1 +
 qapi/migration.json |  8 +++++++-
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/migration/options.c b/migration/options.c
index 8d8ec73ad9..0f6bd78b9f 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -204,6 +204,8 @@ Property migration_properties[] = {
     DEFINE_PROP_MIG_CAP("x-switchover-ack",
                         MIGRATION_CAPABILITY_SWITCHOVER_ACK),
     DEFINE_PROP_MIG_CAP("x-dirty-limit", MIGRATION_CAPABILITY_DIRTY_LIMIT),
+    DEFINE_PROP_MIG_CAP("main-zero-page",
+            MIGRATION_CAPABILITY_MAIN_ZERO_PAGE),
     DEFINE_PROP_END_OF_LIST(),
 };
 
@@ -284,6 +286,19 @@ bool migrate_multifd(void)
     return s->capabilities[MIGRATION_CAPABILITY_MULTIFD];
 }
 
+bool migrate_use_main_zero_page(void)
+{
+    /* MigrationState *s; */
+
+    /* s = migrate_get_current(); */
+
+    /*
+     * We will enable this when we add the right code.
+     * return s->enabled_capabilities[MIGRATION_CAPABILITY_MAIN_ZERO_PAGE];
+     */
+    return true;
+}
+
 bool migrate_pause_before_switchover(void)
 {
     MigrationState *s = migrate_get_current();
diff --git a/migration/options.h b/migration/options.h
index 246c160aee..c901eb57c6 100644
--- a/migration/options.h
+++ b/migration/options.h
@@ -88,6 +88,7 @@ int migrate_multifd_channels(void);
 MultiFDCompression migrate_multifd_compression(void);
 int migrate_multifd_zlib_level(void);
 int migrate_multifd_zstd_level(void);
+bool migrate_use_main_zero_page(void);
 uint8_t migrate_throttle_trigger_threshold(void);
 const char *migrate_tls_authz(void);
 const char *migrate_tls_creds(void);
diff --git a/qapi/migration.json b/qapi/migration.json
index eb2f883513..80c4b13516 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -531,6 +531,12 @@
 #     and can result in more stable read performance.  Requires KVM
 #     with accelerator property "dirty-ring-size" set.  (Since 8.1)
 #
+#
+# @main-zero-page: If enabled, the detection of zero pages will be
+#                  done on the main thread.  Otherwise it is done on
+#                  the multifd threads.
+#                  (since 8.2)
+#
 # Features:
 #
 # @deprecated: Member @block is deprecated.  Use blockdev-mirror with
@@ -555,7 +561,7 @@
            { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
            'validate-uuid', 'background-snapshot',
            'zero-copy-send', 'postcopy-preempt', 'switchover-ack',
-           'dirty-limit'] }
+           'dirty-limit', 'main-zero-page'] }
 
 ##
 # @MigrationCapabilityStatus:
-- 
2.30.2