[PATCH v4 1/7] migration/multifd: Add new migration option zero-page-detection.

[Hao Xiang]

This new parameter controls where the zero page checking is running.
1. If this parameter is set to 'legacy', zero page checking is
done in the migration main thread.
2. If this parameter is set to 'none', zero page checking is disabled.

Signed-off-by: Hao Xiang <hao.xiang@bytedance.com>
---
 hw/core/qdev-properties-system.c    | 10 +++++++++
 include/hw/qdev-properties-system.h |  4 ++++
 migration/migration-hmp-cmds.c      |  9 ++++++++
 migration/options.c                 | 21 ++++++++++++++++++
 migration/options.h                 |  1 +
 migration/ram.c                     |  4 ++++
 qapi/migration.json                 | 33 ++++++++++++++++++++++++++---
 7 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/hw/core/qdev-properties-system.c b/hw/core/qdev-properties-system.c
index 1a396521d5..228e685f52 100644
--- a/hw/core/qdev-properties-system.c
+++ b/hw/core/qdev-properties-system.c
@@ -679,6 +679,16 @@ const PropertyInfo qdev_prop_mig_mode = {
     .set_default_value = qdev_propinfo_set_default_value_enum,
 };
 
+const PropertyInfo qdev_prop_zero_page_detection = {
+    .name = "ZeroPageDetection",
+    .description = "zero_page_detection values, "
+                   "none,legacy",
+    .enum_table = &ZeroPageDetection_lookup,
+    .get = qdev_propinfo_get_enum,
+    .set = qdev_propinfo_set_enum,
+    .set_default_value = qdev_propinfo_set_default_value_enum,
+};
+
 /* --- Reserved Region --- */
 
 /*
diff --git a/include/hw/qdev-properties-system.h 
b/include/hw/qdev-properties-system.h
index 06c359c190..839b170235 100644
--- a/include/hw/qdev-properties-system.h
+++ b/include/hw/qdev-properties-system.h
@@ -8,6 +8,7 @@ extern const PropertyInfo qdev_prop_macaddr;
 extern const PropertyInfo qdev_prop_reserved_region;
 extern const PropertyInfo qdev_prop_multifd_compression;
 extern const PropertyInfo qdev_prop_mig_mode;
+extern const PropertyInfo qdev_prop_zero_page_detection;
 extern const PropertyInfo qdev_prop_losttickpolicy;
 extern const PropertyInfo qdev_prop_blockdev_on_error;
 extern const PropertyInfo qdev_prop_bios_chs_trans;
@@ -47,6 +48,9 @@ extern const PropertyInfo qdev_prop_iothread_vq_mapping_list;
 #define DEFINE_PROP_MIG_MODE(_n, _s, _f, _d) \
     DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_mig_mode, \
                        MigMode)
+#define DEFINE_PROP_ZERO_PAGE_DETECTION(_n, _s, _f, _d) \
+    DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_zero_page_detection, \
+                       ZeroPageDetection)
 #define DEFINE_PROP_LOSTTICKPOLICY(_n, _s, _f, _d) \
     DEFINE_PROP_SIGNED(_n, _s, _f, _d, qdev_prop_losttickpolicy, \
                         LostTickPolicy)
diff --git a/migration/migration-hmp-cmds.c b/migration/migration-hmp-cmds.c
index 99b49df5dd..7e96ae6ffd 100644
--- a/migration/migration-hmp-cmds.c
+++ b/migration/migration-hmp-cmds.c
@@ -344,6 +344,11 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict 
*qdict)
         monitor_printf(mon, "%s: %s\n",
             MigrationParameter_str(MIGRATION_PARAMETER_MULTIFD_COMPRESSION),
             MultiFDCompression_str(params->multifd_compression));
+        assert(params->has_zero_page_detection);
+        monitor_printf(mon, "%s: %s\n",
+            MigrationParameter_str(MIGRATION_PARAMETER_ZERO_PAGE_DETECTION),
+            qapi_enum_lookup(&ZeroPageDetection_lookup,
+                params->zero_page_detection));
         monitor_printf(mon, "%s: %" PRIu64 " bytes\n",
             MigrationParameter_str(MIGRATION_PARAMETER_XBZRLE_CACHE_SIZE),
             params->xbzrle_cache_size);
@@ -634,6 +639,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict 
*qdict)
         p->has_multifd_zstd_level = true;
         visit_type_uint8(v, param, &p->multifd_zstd_level, &err);
         break;
+    case MIGRATION_PARAMETER_ZERO_PAGE_DETECTION:
+        p->has_zero_page_detection = true;
+        visit_type_ZeroPageDetection(v, param, &p->zero_page_detection, &err);
+        break;
     case MIGRATION_PARAMETER_XBZRLE_CACHE_SIZE:
         p->has_xbzrle_cache_size = true;
         if (!visit_type_size(v, param, &cache_size, &err)) {
diff --git a/migration/options.c b/migration/options.c
index 3e3e0b93b4..3c603391b0 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -179,6 +179,9 @@ Property migration_properties[] = {
     DEFINE_PROP_MIG_MODE("mode", MigrationState,
                       parameters.mode,
                       MIG_MODE_NORMAL),
+    DEFINE_PROP_ZERO_PAGE_DETECTION("zero-page-detection", MigrationState,
+                       parameters.zero_page_detection,
+                       ZERO_PAGE_DETECTION_LEGACY),
 
     /* Migration capabilities */
     DEFINE_PROP_MIG_CAP("x-xbzrle", MIGRATION_CAPABILITY_XBZRLE),
@@ -903,6 +906,13 @@ uint64_t migrate_xbzrle_cache_size(void)
     return s->parameters.xbzrle_cache_size;
 }
 
+ZeroPageDetection migrate_zero_page_detection(void)
+{
+    MigrationState *s = migrate_get_current();
+
+    return s->parameters.zero_page_detection;
+}
+
 /* parameter setters */
 
 void migrate_set_block_incremental(bool value)
@@ -1013,6 +1023,8 @@ MigrationParameters *qmp_query_migrate_parameters(Error 
**errp)
     params->vcpu_dirty_limit = s->parameters.vcpu_dirty_limit;
     params->has_mode = true;
     params->mode = s->parameters.mode;
+    params->has_zero_page_detection = true;
+    params->zero_page_detection = s->parameters.zero_page_detection;
 
     return params;
 }
@@ -1049,6 +1061,7 @@ void migrate_params_init(MigrationParameters *params)
     params->has_x_vcpu_dirty_limit_period = true;
     params->has_vcpu_dirty_limit = true;
     params->has_mode = true;
+    params->has_zero_page_detection = true;
 }
 
 /*
@@ -1350,6 +1363,10 @@ static void 
migrate_params_test_apply(MigrateSetParameters *params,
     if (params->has_mode) {
         dest->mode = params->mode;
     }
+
+    if (params->has_zero_page_detection) {
+        dest->zero_page_detection = params->zero_page_detection;
+    }
 }
 
 static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
@@ -1494,6 +1511,10 @@ static void migrate_params_apply(MigrateSetParameters 
*params, Error **errp)
     if (params->has_mode) {
         s->parameters.mode = params->mode;
     }
+
+    if (params->has_zero_page_detection) {
+        s->parameters.zero_page_detection = params->zero_page_detection;
+    }
 }
 
 void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
diff --git a/migration/options.h b/migration/options.h
index 246c160aee..b7c4fb3861 100644
--- a/migration/options.h
+++ b/migration/options.h
@@ -93,6 +93,7 @@ const char *migrate_tls_authz(void);
 const char *migrate_tls_creds(void);
 const char *migrate_tls_hostname(void);
 uint64_t migrate_xbzrle_cache_size(void);
+ZeroPageDetection migrate_zero_page_detection(void);
 
 /* parameters setters */
 
diff --git a/migration/ram.c b/migration/ram.c
index 45a00b45ed..2581ee1e04 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1122,6 +1122,10 @@ static int save_zero_page(RAMState *rs, PageSearchStatus 
*pss,
     QEMUFile *file = pss->pss_channel;
     int len = 0;
 
+    if (migrate_zero_page_detection() == ZERO_PAGE_DETECTION_NONE) {
+        return 0;
+    }
+
     if (!buffer_is_zero(p, TARGET_PAGE_SIZE)) {
         return 0;
     }
diff --git a/qapi/migration.json b/qapi/migration.json
index 0b33a71ab4..8da05dba47 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -664,6 +664,18 @@
 { 'enum': 'MigMode',
   'data': [ 'normal', 'cpr-reboot' ] }
 
+##
+# @ZeroPageDetection:
+#
+# @none: Do not perform zero page checking.
+#
+# @legacy: Perform zero page checking in main migration thread.
+#
+# Since: 9.0
+##
+{ 'enum': 'ZeroPageDetection',
+  'data': [ 'none', 'legacy' ] }
+
 ##
 # @BitmapMigrationBitmapAliasTransform:
 #
@@ -885,6 +897,10 @@
 # @mode: Migration mode. See description in @MigMode. Default is 'normal'.
 #        (Since 8.2)
 #
+# @zero-page-detection: Whether and how to detect zero pages.
+#     See description in @ZeroPageDetection.  Default is 'legacy'.
+#     (since 9.0)
+#
 # Features:
 #
 # @deprecated: Member @block-incremental is deprecated.  Use
@@ -918,7 +934,8 @@
            'block-bitmap-mapping',
            { 'name': 'x-vcpu-dirty-limit-period', 'features': ['unstable'] },
            'vcpu-dirty-limit',
-           'mode'] }
+           'mode',
+           'zero-page-detection'] }
 
 ##
 # @MigrateSetParameters:
@@ -1077,6 +1094,10 @@
 # @mode: Migration mode. See description in @MigMode. Default is 'normal'.
 #        (Since 8.2)
 #
+# @zero-page-detection: Whether and how to detect zero pages.
+#     See description in @ZeroPageDetection.  Default is 'legacy'.
+#     (since 9.0)
+#
 # Features:
 #
 # @deprecated: Member @block-incremental is deprecated.  Use
@@ -1130,7 +1151,8 @@
             '*x-vcpu-dirty-limit-period': { 'type': 'uint64',
                                             'features': [ 'unstable' ] },
             '*vcpu-dirty-limit': 'uint64',
-            '*mode': 'MigMode'} }
+            '*mode': 'MigMode',
+            '*zero-page-detection': 'ZeroPageDetection'} }
 
 ##
 # @migrate-set-parameters:
@@ -1305,6 +1327,10 @@
 # @mode: Migration mode. See description in @MigMode. Default is 'normal'.
 #        (Since 8.2)
 #
+# @zero-page-detection: Whether and how to detect zero pages.
+#     See description in @ZeroPageDetection.  Default is 'legacy'.
+#     (since 9.0)
+#
 # Features:
 #
 # @deprecated: Member @block-incremental is deprecated.  Use
@@ -1355,7 +1381,8 @@
             '*x-vcpu-dirty-limit-period': { 'type': 'uint64',
                                             'features': [ 'unstable' ] },
             '*vcpu-dirty-limit': 'uint64',
-            '*mode': 'MigMode'} }
+            '*mode': 'MigMode',
+            '*zero-page-detection': 'ZeroPageDetection'} }
 
 ##
 # @query-migrate-parameters:
-- 
2.30.2