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>

2 files changed, 33 insertions, 10 deletions

diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
index 04d5ee8fb7..9180cf1841 100644
--- a/monitor/hmp-cmds.c
+++ b/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;
     }
diff --git a/monitor/qmp-cmds.c b/monitor/qmp-cmds.c
index 5f8f1e620b..e49ab345d7 100644
--- a/monitor/qmp-cmds.c
+++ b/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)) {
-            break;
+        if (filter->has_providers) {
+            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 (*errp) {
-            qapi_free_StatsSchemaList(stats_results);
-            return NULL;
+        if (!has_provider || provider == entry->provider) {
+            entry->schemas_cb(&stats_results, errp);
+            if (*errp) {
+                qapi_free_StatsSchemaList(stats_results);
+                return NULL;
+            }
         }
     }