qmp: add filtering of statistics by target vCPU

Introduce a simple filtering of statistics, that allows to retrieve
statistics for a subset of the guest vCPUs.  This will be used for
example by the HMP monitor, in order to retrieve the statistics
for the currently selected CPU.

Example:
{ "execute": "query-stats",
  "arguments": {
    "target": "vcpu",
    "vcpus": [ "/machine/unattached/device[2]",
               "/machine/unattached/device[4]" ] } }

Extracted from a patch by Mark Kanda.

Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 17 insertions, 3 deletions

diff --git a/qapi/stats.json b/qapi/stats.json
index df7c4d8..8c9abb5 100644
--- a/qapi/stats.json
+++ b/qapi/stats.json
@@ -70,15 +70,29 @@
   'data': [ 'vm', 'vcpu' ] }
 
 ##
+# @StatsVCPUFilter:
+#
+# @vcpus: list of QOM paths for the desired vCPU objects.
+#
+# Since: 7.1
+##
+{ 'struct': 'StatsVCPUFilter',
+  'data': { '*vcpus': [ 'str' ] } }
+
+##
 # @StatsFilter:
 #
 # The arguments to the query-stats command; specifies a target for which to
-# request statistics.
+# request statistics and optionally the required subset of information for
+# that target:
+# - which vCPUs to request statistics for
 #
 # Since: 7.1
 ##
-{ 'struct': 'StatsFilter',
-  'data': { 'target': 'StatsTarget' } }
+{ 'union': 'StatsFilter',
+        'base': { 'target': 'StatsTarget' },
+  'discriminator': 'target',
+  'data': { 'vcpu': 'StatsVCPUFilter' } }
 
 ##
 # @StatsValue: