[PATCH v3 3/4] migration: Deprecate block migration

[Juan Quintela <quintela@redhat.com>]

It is obsolete.  It is better to use driver-mirror with NBD instead.

CC: Kevin Wolf <kwolf@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Hanna Czenczek <hreitz@redhat.com>

Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 docs/about/deprecated.rst | 10 ++++++++++
 qapi/migration.json       | 30 +++++++++++++++++++++++++-----
 migration/block.c         |  3 +++
 migration/options.c       |  9 ++++++++-
 4 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index b2b7e11742..e46f3df376 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -431,3 +431,13 @@ The new way to modify migration is using migration parameters.
 ``blk`` functionality can be achieved by setting the
 ``block`` migration capability to ``true``.
 
+block migration (since 8.2)
+'''''''''''''''''''''''''''
+
+Block migration is too inflexible.  It needs to migrate all block
+devices or none.
+
+Please see "QMP invocation for live storage migration with
+``driver-mirror`` + NBD" in docs/interop/live-block-operations.rst for
+a detailed explanation.
+
diff --git a/qapi/migration.json b/qapi/migration.json
index e4949e0d8e..bf6e1ac5b5 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -269,11 +269,16 @@
 #     average memory load of the virtual CPU indirectly.  Note that
 #     zero means guest doesn't dirty memory.  (Since 8.1)
 #
+# Features:
+#
+# @deprecated: @disk migration is deprecated.  Use driver-mirror
+#     with NBD instead.
+#
 # Since: 0.14
 ##
 { 'struct': 'MigrationInfo',
   'data': {'*status': 'MigrationStatus', '*ram': 'MigrationStats',
-           '*disk': 'MigrationStats',
+           '*disk': { 'type': 'MigrationStats', 'features': ['deprecated'] },
            '*vfio': 'VfioStats',
            '*xbzrle-cache': 'XBZRLECacheStats',
            '*total-time': 'int',
@@ -526,6 +531,9 @@
 #
 # Features:
 #
+# @deprecated: @block migration is deprecated.  Use driver-mirror
+#     with NBD instead.
+#
 # @unstable: Members @x-colo and @x-ignore-shared are experimental.
 #
 # Since: 1.2
@@ -535,7 +543,8 @@
            'compress', 'events', 'postcopy-ram',
            { 'name': 'x-colo', 'features': [ 'unstable' ] },
            'release-ram',
-           'block', 'return-path', 'pause-before-switchover', 'multifd',
+           { 'name': 'block', 'features': [ 'deprecated' ] },
+           'return-path', 'pause-before-switchover', 'multifd',
            'dirty-bitmaps', 'postcopy-blocktime', 'late-block-activate',
            { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] },
            'validate-uuid', 'background-snapshot',
@@ -826,6 +835,9 @@
 #
 # Features:
 #
+# @deprecated: Member @block-incremental is obsolete. Use
+#     driver-mirror with NBD instead.
+#
 # @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period
 #     are experimental.
 #
@@ -841,7 +853,7 @@
            'tls-creds', 'tls-hostname', 'tls-authz', 'max-bandwidth',
            'downtime-limit',
            { 'name': 'x-checkpoint-delay', 'features': [ 'unstable' ] },
-           'block-incremental',
+           { 'name': 'block-incremental', 'features': [ 'deprecated' ] },
            'multifd-channels',
            'xbzrle-cache-size', 'max-postcopy-bandwidth',
            'max-cpu-throttle', 'multifd-compression',
@@ -992,6 +1004,9 @@
 #
 # Features:
 #
+# @deprecated: Member @block-incremental is obsolete. Use
+#     driver-mirror with NBD instead.
+#
 # @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period
 #     are experimental.
 #
@@ -1020,7 +1035,8 @@
             '*downtime-limit': 'uint64',
             '*x-checkpoint-delay': { 'type': 'uint32',
                                      'features': [ 'unstable' ] },
-            '*block-incremental': 'bool',
+            '*block-incremental': { 'type': 'bool',
+                                    'features': [ 'deprecated' ] },
             '*multifd-channels': 'uint8',
             '*xbzrle-cache-size': 'size',
             '*max-postcopy-bandwidth': 'size',
@@ -1195,6 +1211,9 @@
 #
 # Features:
 #
+# @deprecated: Member @block-incremental is obsolete. Use
+#     driver-mirror with NBD instead.
+#
 # @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period
 #     are experimental.
 #
@@ -1220,7 +1239,8 @@
             '*downtime-limit': 'uint64',
             '*x-checkpoint-delay': { 'type': 'uint32',
                                      'features': [ 'unstable' ] },
-            '*block-incremental': 'bool',
+            '*block-incremental': { 'type': 'bool',
+                                    'features': [ 'deprecated' ] },
             '*multifd-channels': 'uint8',
             '*xbzrle-cache-size': 'size',
             '*max-postcopy-bandwidth': 'size',
diff --git a/migration/block.c b/migration/block.c
index 5f930870a5..46bb431ed3 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -729,6 +729,9 @@ static int block_save_setup(QEMUFile *f, void *opaque)
     trace_migration_block_save("setup", block_mig_state.submitted,
                                block_mig_state.transferred);
 
+    warn_report("block migration is deprecated.  Use driver-mirror with"
+                "NBD instead.");
+
     qemu_mutex_lock_iothread();
     ret = init_blk_migration(f);
     if (ret < 0) {
diff --git a/migration/options.c b/migration/options.c
index 6bbfd4853d..48cbbd682a 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -12,6 +12,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "exec/target_page.h"
 #include "qapi/clone-visitor.h"
 #include "qapi/error.h"
@@ -464,10 +465,14 @@ bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp)
     if (new_caps[MIGRATION_CAPABILITY_BLOCK]) {
         error_setg(errp, "QEMU compiled without old-style (blk/-b, inc/-i) "
                    "block migration");
-        error_append_hint(errp, "Use drive_mirror+NBD instead.\n");
+        error_append_hint(errp, "Use driver-mirror with NBD instead.\n");
         return false;
     }
 #endif
+    if (new_caps[MIGRATION_CAPABILITY_BLOCK]) {
+        warn_report("Block migration is deprecated. "
+                    "Use driver-mirror with NBD instead.");
+    }
 
 #ifndef CONFIG_REPLICATION
     if (new_caps[MIGRATION_CAPABILITY_X_COLO]) {
@@ -1351,6 +1356,8 @@ static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
     }
 
     if (params->has_block_incremental) {
+        warn_report("Block migration is deprecated. "
+                    "Use driver-mirror with NBD instead.");
         s->parameters.block_incremental = params->block_incremental;
     }
     if (params->has_multifd_channels) {
-- 
2.41.0