[PATCH v7 42/65] virtio-balloon: convert guest-stats property to QAPI type

[Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>]

Define VirtioBalloonStats and VirtioBalloonGuestStats QAPI struct types
in the schema, replacing the hand-rolled visitor in balloon_stats_get_all()
with a generated visit_type_VirtioBalloonGuestStats() call.

The wire format is preserved: the JSON output from qom-get is identical
to the previous hand-rolled visitor output.

Signed-off-by: Markus Armbruster <armbru@xxxxxxxxxx>
Signed-off-by: Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>
---
 docs/interop/virtio-balloon-stats.rst | 22 +--------
 hw/virtio/virtio-balloon.c            | 84 ++++++++++++--------------------
 qapi/machine.json                     | 92 +++++++++++++++++++++++++++++++++++
 3 files changed, 123 insertions(+), 75 deletions(-)

diff --git a/docs/interop/virtio-balloon-stats.rst 
b/docs/interop/virtio-balloon-stats.rst
index b9a6a6edb229..88d3271bbb02 100644
--- a/docs/interop/virtio-balloon-stats.rst
+++ b/docs/interop/virtio-balloon-stats.rst
@@ -22,27 +22,7 @@ polling the guest's balloon driver for new stats in the 
specified time
 interval.
 
 To retrieve those stats, clients have to query the guest-stats property,
-which will return a dictionary containing:
-
-  * A key named 'stats', containing all available stats. If the guest
-    doesn't support a particular stat, or if it couldn't be retrieved,
-    its value will be -1. Currently, the following stats are supported:
-
-      - stat-swap-in
-      - stat-swap-out
-      - stat-major-faults
-      - stat-minor-faults
-      - stat-free-memory
-      - stat-total-memory
-      - stat-available-memory
-      - stat-disk-caches
-      - stat-htlb-pgalloc
-      - stat-htlb-pgfail
-
-  * A key named last-update, which contains the last stats update
-    timestamp in seconds. Since this timestamp is generated by the host,
-    a buggy guest can't influence its value. The value is 0 if the guest
-    has not updated the stats (yet).
+which will return a VirtioBalloonGuestStats (see QAPI documentation).
 
 It's also important to note the following:
 
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 7ffbe48e5134..bfc75f5dfc72 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -29,6 +29,8 @@
 #include "qapi/error.h"
 #include "qapi/qapi-builtin-type-infos.h"
 #include "qapi/qapi-events-machine.h"
+#include "qapi/qapi-type-infos-machine.h"
+#include "qapi/qapi-visit-machine.h"
 #include "qapi/visitor.h"
 #include "trace.h"
 #include "qemu/error-report.h"
@@ -170,33 +172,8 @@ static void balloon_deflate_page(VirtIOBalloon *balloon,
     }
 }
 
-/*
- * All stats upto VIRTIO_BALLOON_S_NR /must/ have a
- * non-NULL name declared here, since these are used
- * as keys for populating the QDict with stats
- */
-static const char *balloon_stat_names[] = {
-   [VIRTIO_BALLOON_S_SWAP_IN] = "stat-swap-in",
-   [VIRTIO_BALLOON_S_SWAP_OUT] = "stat-swap-out",
-   [VIRTIO_BALLOON_S_MAJFLT] = "stat-major-faults",
-   [VIRTIO_BALLOON_S_MINFLT] = "stat-minor-faults",
-   [VIRTIO_BALLOON_S_MEMFREE] = "stat-free-memory",
-
-   [VIRTIO_BALLOON_S_MEMTOT] = "stat-total-memory",
-   [VIRTIO_BALLOON_S_AVAIL] = "stat-available-memory",
-   [VIRTIO_BALLOON_S_CACHES] = "stat-disk-caches",
-   [VIRTIO_BALLOON_S_HTLB_PGALLOC] = "stat-htlb-pgalloc",
-   [VIRTIO_BALLOON_S_HTLB_PGFAIL] = "stat-htlb-pgfail",
-
-   [VIRTIO_BALLOON_S_OOM_KILL] = "stat-oom-kills",
-   [VIRTIO_BALLOON_S_ALLOC_STALL] = "stat-alloc-stalls",
-   [VIRTIO_BALLOON_S_ASYNC_SCAN] = "stat-async-scans",
-   [VIRTIO_BALLOON_S_DIRECT_SCAN] = "stat-direct-scans",
-   [VIRTIO_BALLOON_S_ASYNC_RECLAIM] = "stat-async-reclaims",
-
-   [VIRTIO_BALLOON_S_DIRECT_RECLAIM] = "stat-direct-reclaims",
-};
-G_STATIC_ASSERT(G_N_ELEMENTS(balloon_stat_names) == VIRTIO_BALLOON_S_NR);
+/* Update VirtioBalloonStats QAPI type when new stats are added */
+G_STATIC_ASSERT(VIRTIO_BALLOON_S_NR == 16);
 
 /*
  * reset_stats - Mark all items in the stats array as unset
@@ -258,33 +235,31 @@ static void balloon_stats_get_all(Object *obj, Visitor 
*v, const char *name,
                                   void *opaque, Error **errp)
 {
     VirtIOBalloon *s = VIRTIO_BALLOON(obj);
-    bool ok = false;
-    int i;
+    VirtioBalloonStats stats = {
+        .stat_swap_in = s->stats[VIRTIO_BALLOON_S_SWAP_IN],
+        .stat_swap_out = s->stats[VIRTIO_BALLOON_S_SWAP_OUT],
+        .stat_major_faults = s->stats[VIRTIO_BALLOON_S_MAJFLT],
+        .stat_minor_faults = s->stats[VIRTIO_BALLOON_S_MINFLT],
+        .stat_free_memory = s->stats[VIRTIO_BALLOON_S_MEMFREE],
+        .stat_total_memory = s->stats[VIRTIO_BALLOON_S_MEMTOT],
+        .stat_available_memory = s->stats[VIRTIO_BALLOON_S_AVAIL],
+        .stat_disk_caches = s->stats[VIRTIO_BALLOON_S_CACHES],
+        .stat_htlb_pgalloc = s->stats[VIRTIO_BALLOON_S_HTLB_PGALLOC],
+        .stat_htlb_pgfail = s->stats[VIRTIO_BALLOON_S_HTLB_PGFAIL],
+        .stat_oom_kills = s->stats[VIRTIO_BALLOON_S_OOM_KILL],
+        .stat_alloc_stalls = s->stats[VIRTIO_BALLOON_S_ALLOC_STALL],
+        .stat_async_scans = s->stats[VIRTIO_BALLOON_S_ASYNC_SCAN],
+        .stat_direct_scans = s->stats[VIRTIO_BALLOON_S_DIRECT_SCAN],
+        .stat_async_reclaims = s->stats[VIRTIO_BALLOON_S_ASYNC_RECLAIM],
+        .stat_direct_reclaims = s->stats[VIRTIO_BALLOON_S_DIRECT_RECLAIM],
+    };
+    VirtioBalloonGuestStats guest_stats = {
+        .last_update = s->stats_last_update,
+        .stats = &stats,
+    };
+    VirtioBalloonGuestStats *argp = &guest_stats;
 
-    if (!visit_start_struct(v, name, NULL, 0, errp)) {
-        return;
-    }
-    if (!visit_type_int(v, "last-update", &s->stats_last_update, errp)) {
-        goto out_end;
-    }
-
-    if (!visit_start_struct(v, "stats", NULL, 0, errp)) {
-        goto out_end;
-    }
-    for (i = 0; i < VIRTIO_BALLOON_S_NR; i++) {
-        if (!visit_type_uint64(v, balloon_stat_names[i], &s->stats[i], errp)) {
-            goto out_nested;
-        }
-    }
-    ok = visit_check_struct(v, errp);
-out_nested:
-    visit_end_struct(v, NULL);
-
-    if (ok) {
-        visit_check_struct(v, errp);
-    }
-out_end:
-    visit_end_struct(v, NULL);
+    visit_type_VirtioBalloonGuestStats(v, name, &argp, errp);
 }
 
 static void balloon_stats_get_poll_interval(Object *obj, Visitor *v,
@@ -1037,7 +1012,8 @@ static void virtio_balloon_instance_init(Object *obj)
     s->free_page_hint_cmd_id = VIRTIO_BALLOON_FREE_PAGE_HINT_CMD_ID_MIN;
     s->free_page_hint_notify.notify = virtio_balloon_free_page_hint_notify;
 
-    object_property_add(obj, "guest-stats", "guest statistics",
+    object_property_add_qapi(obj, "guest-stats",
+                        &VirtioBalloonGuestStats_type_info,
                         balloon_stats_get_all, NULL, NULL, NULL);
 
     object_property_add_qapi(obj, "guest-stats-polling-interval", 
&int_type_info,
diff --git a/qapi/machine.json b/qapi/machine.json
index 9b145c635baf..34be3156270c 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1126,6 +1126,98 @@
 ##
 { 'struct': 'BalloonInfo', 'data': {'actual': 'int' } }
 
+##
+# @VirtioBalloonStats:
+#
+# VirtIO balloon device guest memory statistics.
+#
+# If the guest doesn't support a particular stat, or if it couldn't
+# be retrieved, its value will be -1.
+#
+# @stat-swap-in: The amount of memory that has been
+#     swapped in (in bytes).
+#
+# @stat-swap-out: The amount of memory that has been
+#     swapped out to disk (in bytes).
+#
+# @stat-major-faults: The number of major page faults
+#     that have occurred.
+#
+# @stat-minor-faults: The number of minor page faults
+#     that have occurred.
+#
+# @stat-free-memory: The amount of memory not being used
+#     for any purpose (in bytes).
+#
+# @stat-total-memory: The total amount of memory available
+#     (in bytes).
+#
+# @stat-available-memory: An estimate of how much memory is available
+#     (in bytes) for starting new applications, without pushing the
+#     system to swap.
+#
+# @stat-disk-caches: The amount of memory, in bytes, that can be
+#     quickly reclaimed without additional I/O.  Typically these pages
+#     are used for caching files from disk.
+#
+# @stat-htlb-pgalloc: The number of successful hugetlb page
+#     allocations
+#
+# @stat-htlb-pgfail: The number of failed hugetlb page
+#     allocations
+#
+# @stat-oom-kills: The number of OOM killer invocations
+#
+# @stat-alloc-stalls: The number of memory allocation stalls
+#
+# @stat-async-scans: The number of memory scanned asynchronously
+#
+# @stat-direct-scans: The number of memory scanned directly
+#
+# @stat-async-reclaims: The number of memory reclaimed asynchronously
+#
+# @stat-direct-reclaims: The number of memory reclaimed directly
+#
+# Since: 11.2
+##
+{ 'struct': 'VirtioBalloonStats',
+  'data': {
+    'stat-swap-in': 'uint64',
+    'stat-swap-out': 'uint64',
+    'stat-major-faults': 'uint64',
+    'stat-minor-faults': 'uint64',
+    'stat-free-memory': 'uint64',
+    'stat-total-memory': 'uint64',
+    'stat-available-memory': 'uint64',
+    'stat-disk-caches': 'uint64',
+    'stat-htlb-pgalloc': 'uint64',
+    'stat-htlb-pgfail': 'uint64',
+    'stat-oom-kills': 'uint64',
+    'stat-alloc-stalls': 'uint64',
+    'stat-async-scans': 'uint64',
+    'stat-direct-scans': 'uint64',
+    'stat-async-reclaims': 'uint64',
+    'stat-direct-reclaims': 'uint64' } }
+
+##
+# @VirtioBalloonGuestStats:
+#
+# Guest statistics from the VirtIO balloon device.
+#
+# @last-update: timestamp in seconds of the last stats
+#     update from the guest (since this timestamp is generated
+#     by the host, a buggy guest can't influence its value),
+#     or 0 if no update has been received yet.
+#
+# @stats: balloon memory statistics
+#
+# Since: 11.2
+##
+{ 'struct': 'VirtioBalloonGuestStats',
+  'data': {
+    'last-update': 'int',
+    'stats': 'VirtioBalloonStats' } }
+
 ##
 # @query-balloon:
 #     Return information about the balloon device.

-- 
2.56.0.116.g6de20f6092dc