qmp: add filtering of statistics by provider

Allow retrieving the statistics from a specific provider only.
This can be used in the future by HMP commands such as "info
sync-profile" or "info profile".  The next patch also adds
filter-by-provider capabilities to the HMP equivalent of
query-stats, "info stats".

Example:

{ "execute": "query-stats",
  "arguments": {
    "target": "vm",
    "providers": [
      { "provider": "kvm" } ] } }

The QAPI is a bit more verbose than just a list of StatsProvider,
so that it can be subsequently extended with filtering of statistics
by name.

If a provider is specified more than once in the filter, each request
will be included separately in the output.

Extracted from a patch by Mark Kanda.

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

accel/kvm/kvm-all.c

@@ -2644,7 +2644,8 @@ static int kvm_init(MachineState *ms)
     }
 
     if (kvm_check_extension(kvm_state, KVM_CAP_BINARY_STATS_FD)) {
-        add_stats_callbacks(query_stats_cb, query_stats_schemas_cb);
+        add_stats_callbacks(STATS_PROVIDER_KVM, query_stats_cb,
+                            query_stats_schemas_cb);
     }
 
     return 0;

include/monitor/stats.h

@@ -17,10 +17,12 @@ typedef void SchemaRetrieveFunc(StatsSchemaList **result, Error **errp);
 /*
  * Register callbacks for the QMP query-stats command.
  *
+ * @provider: stats provider checked against QMP command arguments
  * @stats_fn: routine to query stats:
  * @schema_fn: routine to query stat schemas:
  */
-void add_stats_callbacks(StatRetrieveFunc *stats_fn,
+void add_stats_callbacks(StatsProvider provider,
+                         StatRetrieveFunc *stats_fn,
                          SchemaRetrieveFunc *schemas_fn);
 
 /*

monitor/hmp-cmds.c

@@ -2397,7 +2397,7 @@ void hmp_info_stats(Monitor *mon, const QDict *qdict)
         goto exit_no_print;
     }
 
-    schema = qmp_query_stats_schemas(&err);
+    schema = qmp_query_stats_schemas(false, STATS_PROVIDER__MAX, &err);
     if (err) {
         goto exit;
     }

monitor/qmp-cmds.c

@@ -445,6 +445,7 @@ HumanReadableText *qmp_x_query_irq(Error **errp)
 }
 
 typedef struct StatsCallbacks {
+    StatsProvider provider;
     StatRetrieveFunc *stats_cb;
     SchemaRetrieveFunc *schemas_cb;
     QTAILQ_ENTRY(StatsCallbacks) next;
@@ -453,10 +454,12 @@ typedef struct StatsCallbacks {
 static QTAILQ_HEAD(, StatsCallbacks) stats_callbacks =
     QTAILQ_HEAD_INITIALIZER(stats_callbacks);
 
-void add_stats_callbacks(StatRetrieveFunc *stats_fn,
+void add_stats_callbacks(StatsProvider provider,
+                         StatRetrieveFunc *stats_fn,
                          SchemaRetrieveFunc *schemas_fn)
 {
     StatsCallbacks *entry = g_new(StatsCallbacks, 1);
+    entry->provider = provider;
     entry->stats_cb = stats_fn;
     entry->schemas_cb = schemas_fn;
 
@@ -465,12 +468,18 @@ void add_stats_callbacks(StatRetrieveFunc *stats_fn,
 
 static bool invoke_stats_cb(StatsCallbacks *entry,
                             StatsResultList **stats_results,
-                            StatsFilter *filter,
+                            StatsFilter *filter, StatsRequest *request,
                             Error **errp)
 {
     strList *targets = NULL;
     ERRP_GUARD();
 
+    if (request) {
+        if (request->provider != entry->provider) {
+            return true;
+        }
+    }
+
     switch (filter->target) {
     case STATS_TARGET_VM:
         break;
@@ -500,27 +509,41 @@ StatsResultList *qmp_query_stats(StatsFilter *filter, Error **errp)
 {
     StatsResultList *stats_results = NULL;
     StatsCallbacks *entry;
+    StatsRequestList *request;
 
     QTAILQ_FOREACH(entry, &stats_callbacks, next) {
-        if (!invoke_stats_cb(entry, &stats_results, filter, errp)) {
+        if (filter->has_providers) {
-            break;
+            for (request = filter->providers; request; request = request->next) {
+                if (!invoke_stats_cb(entry, &stats_results, filter,
+                                     request->value, errp)) {
+                    break;
+                }
+            }
+        } else {
+            if (!invoke_stats_cb(entry, &stats_results, filter, NULL, errp)) {
+                break;
+            }
         }
     }
 
     return stats_results;
 }
 
-StatsSchemaList *qmp_query_stats_schemas(Error **errp)
+StatsSchemaList *qmp_query_stats_schemas(bool has_provider,
+                                         StatsProvider provider,
+                                         Error **errp)
 {
     StatsSchemaList *stats_results = NULL;
     StatsCallbacks *entry;
     ERRP_GUARD();
 
     QTAILQ_FOREACH(entry, &stats_callbacks, next) {
-        entry->schemas_cb(&stats_results, errp);
+        if (!has_provider || provider == entry->provider) {
-        if (*errp) {
+            entry->schemas_cb(&stats_results, errp);
-            qapi_free_StatsSchemaList(stats_results);
+            if (*errp) {
-            return NULL;
+                qapi_free_StatsSchemaList(stats_results);
+                return NULL;
+            }
         }
     }
 

qapi/stats.json

@@ -69,6 +69,18 @@
 { 'enum': 'StatsTarget',
   'data': [ 'vm', 'vcpu' ] }
 
+##
+# @StatsRequest:
+#
+# Indicates a set of statistics that should be returned by query-stats.
+#
+# @provider: provider for which to return statistics.
+#
+# Since: 7.1
+##
+{ 'struct': 'StatsRequest',
+  'data': { 'provider': 'StatsProvider' } }
+
 ##
 # @StatsVCPUFilter:
 #
@@ -86,11 +98,14 @@
 # request statistics and optionally the required subset of information for
 # that target:
 # - which vCPUs to request statistics for
+# - which providers to request statistics from
 #
 # Since: 7.1
 ##
 { 'union': 'StatsFilter',
-        'base': { 'target': 'StatsTarget' },
+  'base': {
+      'target': 'StatsTarget',
+      '*providers': [ 'StatsRequest' ] },
   'discriminator': 'target',
   'data': { 'vcpu': 'StatsVCPUFilter' } }
 
@@ -226,5 +241,5 @@
 # Since: 7.1
 ##
 { 'command': 'query-stats-schemas',
-  'data': { },
+  'data': { '*provider': 'StatsProvider' },
   'returns': [ 'StatsSchema' ] }