[Qemu-devel] [PATCH] migration: introduce decompress-error-check

[guangrong . xiao]

From: Xiao Guangrong <address@hidden>

QEMU 2.13 enables strict check for compression & decompression to
make the migration more robuster, that depends on the source to fix
the internal design which triggers the unexpected error conditions

To make it work for migrating old version QEMU to 2.13 QEMU, we
introduce this parameter to disable the error check on the
destination

Signed-off-by: Xiao Guangrong <address@hidden>
---
 hmp.c                 |  8 ++++++++
 migration/migration.c | 19 +++++++++++++++++++
 migration/migration.h |  1 +
 migration/ram.c       |  2 +-
 qapi/migration.json   | 43 +++++++++++++++++++++++++++++++++++++++----
 5 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/hmp.c b/hmp.c
index 898e25f3e1..f0b934368b 100644
--- a/hmp.c
+++ b/hmp.c
@@ -329,6 +329,10 @@ void hmp_info_migrate_parameters(Monitor *mon, const QDict 
*qdict)
         monitor_printf(mon, "%s: %u\n",
             MigrationParameter_str(MIGRATION_PARAMETER_DECOMPRESS_THREADS),
             params->decompress_threads);
+        assert(params->has_decompress_error_check);
+        monitor_printf(mon, "%s: %s\n",
+            MigrationParameter_str(MIGRATION_PARAMETER_DECOMPRESS_ERROR_CHECK),
+            params->decompress_error_check ? "on" : "off");
         assert(params->has_cpu_throttle_initial);
         monitor_printf(mon, "%s: %u\n",
             MigrationParameter_str(MIGRATION_PARAMETER_CPU_THROTTLE_INITIAL),
@@ -1593,6 +1597,10 @@ void hmp_migrate_set_parameter(Monitor *mon, const QDict 
*qdict)
         p->has_decompress_threads = true;
         visit_type_int(v, param, &p->decompress_threads, &err);
         break;
+    case MIGRATION_PARAMETER_DECOMPRESS_ERROR_CHECK:
+        p->has_decompress_error_check = true;
+        visit_type_bool(v, param, &p->decompress_error_check, &err);
+        break;
     case MIGRATION_PARAMETER_CPU_THROTTLE_INITIAL:
         p->has_cpu_throttle_initial = true;
         visit_type_int(v, param, &p->cpu_throttle_initial, &err);
diff --git a/migration/migration.c b/migration/migration.c
index 0bdb28e144..1eef084763 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -534,6 +534,8 @@ MigrationParameters *qmp_query_migrate_parameters(Error 
**errp)
     params->compress_threads = s->parameters.compress_threads;
     params->has_decompress_threads = true;
     params->decompress_threads = s->parameters.decompress_threads;
+    params->has_decompress_error_check = true;
+    params->decompress_error_check = s->parameters.decompress_error_check;
     params->has_cpu_throttle_initial = true;
     params->cpu_throttle_initial = s->parameters.cpu_throttle_initial;
     params->has_cpu_throttle_increment = true;
@@ -917,6 +919,10 @@ static void migrate_params_test_apply(MigrateSetParameters 
*params,
         dest->decompress_threads = params->decompress_threads;
     }
 
+    if (params->has_decompress_error_check) {
+        dest->decompress_error_check = params->decompress_error_check;
+    }
+
     if (params->has_cpu_throttle_initial) {
         dest->cpu_throttle_initial = params->cpu_throttle_initial;
     }
@@ -979,6 +985,10 @@ static void migrate_params_apply(MigrateSetParameters 
*params, Error **errp)
         s->parameters.decompress_threads = params->decompress_threads;
     }
 
+    if (params->has_decompress_error_check) {
+        s->parameters.decompress_error_check = params->decompress_error_check;
+    }
+
     if (params->has_cpu_throttle_initial) {
         s->parameters.cpu_throttle_initial = params->cpu_throttle_initial;
     }
@@ -1620,6 +1630,15 @@ int migrate_decompress_threads(void)
     return s->parameters.decompress_threads;
 }
 
+bool migrate_decompress_error_check(void)
+{
+    MigrationState *s;
+
+    s = migrate_get_current();
+
+    return s->parameters.decompress_error_check;
+}
+
 bool migrate_dirty_bitmaps(void)
 {
     MigrationState *s;
diff --git a/migration/migration.h b/migration/migration.h
index 7c69598c54..5efbbaf9d8 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -241,6 +241,7 @@ bool migrate_use_compression(void);
 int migrate_compress_level(void);
 int migrate_compress_threads(void);
 int migrate_decompress_threads(void);
+bool migrate_decompress_error_check(void);
 bool migrate_use_events(void);
 bool migrate_postcopy_blocktime(void);
 
diff --git a/migration/ram.c b/migration/ram.c
index 912810c18e..01cc815410 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2581,7 +2581,7 @@ static void *do_data_decompress(void *opaque)
 
             ret = qemu_uncompress_data(&param->stream, des, pagesize,
                                        param->compbuf, len);
-            if (ret < 0) {
+            if (ret < 0 && migrate_decompress_error_check()) {
                 error_report("decompress data failed");
                 qemu_file_set_error(decomp_file, ret);
             }
diff --git a/qapi/migration.json b/qapi/migration.json
index f3974c6807..68222358e1 100644
--- a/qapi/migration.json
+++ b/qapi/migration.json
@@ -455,6 +455,17 @@
 #          compression, so set the decompress-threads to the number about 1/4
 #          of compress-threads is adequate.
 #
+# @decompress-error-check: check decompression errors. When false, the errors
+#                          triggered by memory decompression are ignored.
+#                          When true, migration is aborted if the errors are
+#                          detected. For the old QEMU versions (< 2.13) the
+#                          internal design will cause decompression to fail
+#                          so the destination should completely ignore the
+#                          error conditions, i.e, make it be false if these
+#                          QEMUs are going to be migrated. Since 2.13, this
+#                          design is fixed, make it be true to avoid corrupting
+#                          the VM silently (Since 2.13)
+#
 # @cpu-throttle-initial: Initial percentage of time guest cpus are throttled
 #                        when migration auto-converge is activated. The
 #                        default value is 20. (Since 2.7)
@@ -511,10 +522,10 @@
 ##
 { 'enum': 'MigrationParameter',
   'data': ['compress-level', 'compress-threads', 'decompress-threads',
-           'cpu-throttle-initial', 'cpu-throttle-increment',
-           'tls-creds', 'tls-hostname', 'max-bandwidth',
-           'downtime-limit', 'x-checkpoint-delay', 'block-incremental',
-           'x-multifd-channels', 'x-multifd-page-count',
+           'decompress-error-check', 'cpu-throttle-initial',
+           'cpu-throttle-increment', 'tls-creds', 'tls-hostname',
+           'max-bandwidth', 'downtime-limit', 'x-checkpoint-delay',
+           'block-incremental', 'x-multifd-channels', 'x-multifd-page-count',
            'xbzrle-cache-size' ] }
 
 ##
@@ -526,6 +537,17 @@
 #
 # @decompress-threads: decompression thread count
 #
+# @decompress-error-check: check decompression errors. When false, the errors
+#                          triggered by memory decompression are ignored.
+#                          When true, migration is aborted if the errors are
+#                          detected. For the old QEMU versions (< 2.13) the
+#                          internal design will cause decompression to fail
+#                          so the destination should completely ignore the
+#                          error conditions, i.e, make it be false if these
+#                          QEMUs are going to be migrated. Since 2.13, this
+#                          design is fixed, make it be true to avoid corrupting
+#                          the VM silently (Since 2.13)
+#
 # @cpu-throttle-initial: Initial percentage of time guest cpus are
 #                        throttled when migration auto-converge is activated.
 #                        The default value is 20. (Since 2.7)
@@ -591,6 +613,7 @@
   'data': { '*compress-level': 'int',
             '*compress-threads': 'int',
             '*decompress-threads': 'int',
+            '*decompress-error-check': 'bool',
             '*cpu-throttle-initial': 'int',
             '*cpu-throttle-increment': 'int',
             '*tls-creds': 'StrOrNull',
@@ -630,6 +653,17 @@
 #
 # @decompress-threads: decompression thread count
 #
+# @decompress-error-check: check decompression errors. When false, the errors
+#                          triggered by memory decompression are ignored.
+#                          When true, migration is aborted if the errors are
+#                          detected. For the old QEMU versions (< 2.13) the
+#                          internal design will cause decompression to fail
+#                          so the destination should completely ignore the
+#                          error conditions, i.e, make it be false if these
+#                          QEMUs are going to be migrated. Since 2.13, this
+#                          design is fixed, make it be true to avoid corrupting
+#                          the VM silently (Since 2.13)
+#
 # @cpu-throttle-initial: Initial percentage of time guest cpus are
 #                        throttled when migration auto-converge is activated.
 #                        (Since 2.7)
@@ -690,6 +724,7 @@
   'data': { '*compress-level': 'uint8',
             '*compress-threads': 'uint8',
             '*decompress-threads': 'uint8',
+            '*decompress-error-check': 'bool',
             '*cpu-throttle-initial': 'uint8',
             '*cpu-throttle-increment': 'uint8',
             '*tls-creds': 'str',
-- 
2.14.3