qapi: Convert query-balloon

Please, note that some of the code supporting memory statistics is
still around (eg. virtio_balloon_receive_stats() and reset_stats()).

Also, the qmp_query_balloon() function is synchronous and thus doesn't
make any use of the (not fully working) monitor's asynchronous command
support (the old non-qapi implementation did).

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

8 files changed, 120 insertions, 138 deletions

diff --git a/balloon.c b/balloon.c
index a2133dba75..e1cd5fac4c 100644
--- a/balloon.c
+++ b/balloon.c
@@ -25,12 +25,11 @@
  */
 
 #include "monitor.h"
-#include "qjson.h"
-#include "qint.h"
 #include "cpu-common.h"
 #include "kvm.h"
 #include "balloon.h"
 #include "trace.h"
+#include "qmp-commands.h"
 
 static QEMUBalloonEvent *balloon_event_fn;
 static QEMUBalloonStatus *balloon_stat_fn;
@@ -72,76 +71,33 @@ static int qemu_balloon(ram_addr_t target)
     return 1;
 }
 
-static int qemu_balloon_status(MonitorCompletion cb, void *opaque)
+static int qemu_balloon_status(BalloonInfo *info)
 {
     if (!balloon_stat_fn) {
         return 0;
     }
-    balloon_stat_fn(balloon_opaque, cb, opaque);
+    balloon_stat_fn(balloon_opaque, info);
     return 1;
 }
 
-static void print_balloon_stat(const char *key, QObject *obj, void *opaque)
+BalloonInfo *qmp_query_balloon(Error **errp)
 {
-    Monitor *mon = opaque;
-
-    if (strcmp(key, "actual")) {
-        monitor_printf(mon, ",%s=%" PRId64, key,
-                       qint_get_int(qobject_to_qint(obj)));
-    }
-}
-
-void monitor_print_balloon(Monitor *mon, const QObject *data)
-{
-    QDict *qdict;
-
-    qdict = qobject_to_qdict(data);
-    if (!qdict_haskey(qdict, "actual")) {
-        return;
-    }
-    monitor_printf(mon, "balloon: actual=%" PRId64,
-                   qdict_get_int(qdict, "actual") >> 20);
-    qdict_iter(qdict, print_balloon_stat, mon);
-    monitor_printf(mon, "\n");
-}
-
-/**
- * do_info_balloon(): Balloon information
- *
- * Make an asynchronous request for balloon info.  When the request completes
- * a QDict will be returned according to the following specification:
- *
- * - "actual": current balloon value in bytes
- * The following fields may or may not be present:
- * - "mem_swapped_in": Amount of memory swapped in (bytes)
- * - "mem_swapped_out": Amount of memory swapped out (bytes)
- * - "major_page_faults": Number of major faults
- * - "minor_page_faults": Number of minor faults
- * - "free_mem": Total amount of free and unused memory (bytes)
- * - "total_mem": Total amount of available memory (bytes)
- *
- * Example:
- *
- * { "actual": 1073741824, "mem_swapped_in": 0, "mem_swapped_out": 0,
- *   "major_page_faults": 142, "minor_page_faults": 239245,
- *   "free_mem": 1014185984, "total_mem": 1044668416 }
- */
-int do_info_balloon(Monitor *mon, MonitorCompletion cb, void *opaque)
-{
-    int ret;
+    BalloonInfo *info;
 
     if (kvm_enabled() && !kvm_has_sync_mmu()) {
-        qerror_report(QERR_KVM_MISSING_CAP, "synchronous MMU", "balloon");
-        return -1;
+        error_set(errp, QERR_KVM_MISSING_CAP, "synchronous MMU", "balloon");
+        return NULL;
     }
 
-    ret = qemu_balloon_status(cb, opaque);
-    if (!ret) {
-        qerror_report(QERR_DEVICE_NOT_ACTIVE, "balloon");
-        return -1;
+    info = g_malloc0(sizeof(*info));
+
+    if (qemu_balloon_status(info) == 0) {
+        error_set(errp, QERR_DEVICE_NOT_ACTIVE, "balloon");
+        qapi_free_BalloonInfo(info);
+        return NULL;
     }
 
-    return 0;
+    return info;
 }
 
 /**
diff --git a/balloon.h b/balloon.h
index f59e2881f6..b36abeadf0 100644
--- a/balloon.h
+++ b/balloon.h
@@ -15,17 +15,15 @@
 #define _QEMU_BALLOON_H
 
 #include "monitor.h"
+#include "qapi-types.h"
 
 typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
-typedef void (QEMUBalloonStatus)(void *opaque, MonitorCompletion cb,
-                                 void *cb_data);
+typedef void (QEMUBalloonStatus)(void *opaque, BalloonInfo *info);
 
 int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
 			     QEMUBalloonStatus *stat_func, void *opaque);
 void qemu_remove_balloon_handler(void *opaque);
 
-void monitor_print_balloon(Monitor *mon, const QObject *data);
-int do_info_balloon(Monitor *mon, MonitorCompletion cb, void *opaque);
 int do_balloon(Monitor *mon, const QDict *params,
                MonitorCompletion cb, void *opaque);
 
diff --git a/hmp.c b/hmp.c
index aae13c093b..e0b40b16e5 100644
--- a/hmp.c
+++ b/hmp.c
@@ -349,6 +349,45 @@ out:
     qapi_free_SpiceInfo(info);
 }
 
+void hmp_info_balloon(Monitor *mon)
+{
+    BalloonInfo *info;
+    Error *err = NULL;
+
+    info = qmp_query_balloon(&err);
+    if (err) {
+        monitor_printf(mon, "%s\n", error_get_pretty(err));
+        error_free(err);
+        return;
+    }
+
+    monitor_printf(mon, "balloon: actual=%" PRId64, info->actual >> 20);
+    if (info->has_mem_swapped_in) {
+        monitor_printf(mon, " mem_swapped_in=%" PRId64, info->mem_swapped_in);
+    }
+    if (info->has_mem_swapped_out) {
+        monitor_printf(mon, " mem_swapped_out=%" PRId64, info->mem_swapped_out);
+    }
+    if (info->has_major_page_faults) {
+        monitor_printf(mon, " major_page_faults=%" PRId64,
+                       info->major_page_faults);
+    }
+    if (info->has_minor_page_faults) {
+        monitor_printf(mon, " minor_page_faults=%" PRId64,
+                       info->minor_page_faults);
+    }
+    if (info->has_free_mem) {
+        monitor_printf(mon, " free_mem=%" PRId64, info->free_mem);
+    }
+    if (info->has_total_mem) {
+        monitor_printf(mon, " total_mem=%" PRId64, info->total_mem);
+    }
+
+    monitor_printf(mon, "\n");
+
+    qapi_free_BalloonInfo(info);
+}
+
 void hmp_quit(Monitor *mon, const QDict *qdict)
 {
     monitor_suspend(mon);
diff --git a/hmp.h b/hmp.h
index 09f3a01cee..d2c2d88795 100644
--- a/hmp.h
+++ b/hmp.h
@@ -30,6 +30,7 @@ void hmp_info_block(Monitor *mon);
 void hmp_info_blockstats(Monitor *mon);
 void hmp_info_vnc(Monitor *mon);
 void hmp_info_spice(Monitor *mon);
+void hmp_info_balloon(Monitor *mon);
 void hmp_quit(Monitor *mon, const QDict *qdict);
 void hmp_stop(Monitor *mon, const QDict *qdict);
 void hmp_system_reset(Monitor *mon, const QDict *qdict);
diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index 5f8f4bdb9f..e24a2bf1f3 100644
--- a/hw/virtio-balloon.c
+++ b/hw/virtio-balloon.c
@@ -18,22 +18,14 @@
 #include "virtio.h"
 #include "pc.h"
 #include "cpu.h"
-#include "monitor.h"
 #include "balloon.h"
 #include "virtio-balloon.h"
 #include "kvm.h"
-#include "qlist.h"
-#include "qint.h"
-#include "qstring.h"
 
 #if defined(__linux__)
 #include <sys/mman.h>
 #endif
 
-/* Disable guest-provided stats by now (https://bugzilla.redhat.com/show_bug.cgi?id=623903) */
-#define ENABLE_GUEST_STATS   0
-
-
 typedef struct VirtIOBalloon
 {
     VirtIODevice vdev;
@@ -43,8 +35,6 @@ typedef struct VirtIOBalloon
     uint64_t stats[VIRTIO_BALLOON_S_NR];
     VirtQueueElement stats_vq_elem;
     size_t stats_vq_offset;
-    MonitorCompletion *stats_callback;
-    void *stats_opaque_callback_data;
     DeviceState *qdev;
 } VirtIOBalloon;
 
@@ -76,31 +66,6 @@ static inline void reset_stats(VirtIOBalloon *dev)
     for (i = 0; i < VIRTIO_BALLOON_S_NR; dev->stats[i++] = -1);
 }
 
-static void stat_put(QDict *dict, const char *label, uint64_t val)
-{
-    if (val != -1)
-        qdict_put(dict, label, qint_from_int(val));
-}
-
-static QObject *get_stats_qobject(VirtIOBalloon *dev)
-{
-    QDict *dict = qdict_new();
-    uint64_t actual = ram_size - ((uint64_t) dev->actual <<
-                                  VIRTIO_BALLOON_PFN_SHIFT);
-
-    stat_put(dict, "actual", actual);
-#if ENABLE_GUEST_STATS
-    stat_put(dict, "mem_swapped_in", dev->stats[VIRTIO_BALLOON_S_SWAP_IN]);
-    stat_put(dict, "mem_swapped_out", dev->stats[VIRTIO_BALLOON_S_SWAP_OUT]);
-    stat_put(dict, "major_page_faults", dev->stats[VIRTIO_BALLOON_S_MAJFLT]);
-    stat_put(dict, "minor_page_faults", dev->stats[VIRTIO_BALLOON_S_MINFLT]);
-    stat_put(dict, "free_mem", dev->stats[VIRTIO_BALLOON_S_MEMFREE]);
-    stat_put(dict, "total_mem", dev->stats[VIRTIO_BALLOON_S_MEMTOT]);
-#endif
-
-    return QOBJECT(dict);
-}
-
 static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 {
     VirtIOBalloon *s = to_virtio_balloon(vdev);
@@ -131,20 +96,6 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
     }
 }
 
-static void complete_stats_request(VirtIOBalloon *vb)
-{
-    QObject *stats;
-
-    if (!vb->stats_opaque_callback_data)
-        return;
-
-    stats = get_stats_qobject(vb);
-    vb->stats_callback(vb->stats_opaque_callback_data, stats);
-    qobject_decref(stats);
-    vb->stats_opaque_callback_data = NULL;
-    vb->stats_callback = NULL;
-}
-
 static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq)
 {
     VirtIOBalloon *s = DO_UPCAST(VirtIOBalloon, vdev, vdev);
@@ -172,8 +123,6 @@ static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq)
             s->stats[tag] = val;
     }
     s->stats_vq_offset = offset;
-
-    complete_stats_request(s);
 }
 
 static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
@@ -202,32 +151,33 @@ static uint32_t virtio_balloon_get_features(VirtIODevice *vdev, uint32_t f)
     return f;
 }
 
-static void virtio_balloon_stat(void *opaque, MonitorCompletion cb,
-                                void *cb_data)
+static void virtio_balloon_stat(void *opaque, BalloonInfo *info)
 {
     VirtIOBalloon *dev = opaque;
 
-    /* For now, only allow one request at a time.  This restriction can be
-     * removed later by queueing callback and data pairs.
+#if 0
+    /* Disable guest-provided stats for now. For more details please check:
+     * https://bugzilla.redhat.com/show_bug.cgi?id=623903
+     *
+     * If you do enable it (which is probably not going to happen as we
+     * need a new command for it), remember that you also need to fill the
+     * appropriate members of the BalloonInfo structure so that the stats
+     * are returned to the client.
      */
-    if (dev->stats_callback != NULL) {
-        return;
-    }
-    dev->stats_callback = cb;
-    dev->stats_opaque_callback_data = cb_data;
-
-    if (ENABLE_GUEST_STATS
-        && (dev->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ))) {
+    if (dev->vdev.guest_features & (1 << VIRTIO_BALLOON_F_STATS_VQ)) {
         virtqueue_push(dev->svq, &dev->stats_vq_elem, dev->stats_vq_offset);
         virtio_notify(&dev->vdev, dev->svq);
         return;
     }
+#endif
 
     /* Stats are not supported.  Clear out any stale values that might
      * have been set by a more featureful guest kernel.
      */
     reset_stats(dev);
-    complete_stats_request(dev);
+
+    info->actual = ram_size - ((uint64_t) dev->actual <<
+                               VIRTIO_BALLOON_PFN_SHIFT);
 }
 
 static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
diff --git a/monitor.c b/monitor.c
index fc3da382f0..379b7d4a58 100644
--- a/monitor.c
+++ b/monitor.c
@@ -2904,9 +2904,7 @@ static const mon_cmd_t info_cmds[] = {
         .args_type  = "",
         .params     = "",
         .help       = "show balloon information",
-        .user_print = monitor_print_balloon,
-        .mhandler.info_async = do_info_balloon,
-        .flags      = MONITOR_CMD_ASYNC,
+        .mhandler.info = hmp_info_balloon,
     },
     {
         .name       = "qtree",
@@ -2964,15 +2962,6 @@ static const mon_cmd_t qmp_query_cmds[] = {
         .user_print = do_pci_info_print,
         .mhandler.info_new = do_pci_info,
     },
-    {
-        .name       = "balloon",
-        .args_type  = "",
-        .params     = "",
-        .help       = "show balloon information",
-        .user_print = monitor_print_balloon,
-        .mhandler.info_async = do_info_balloon,
-        .flags      = MONITOR_CMD_ASYNC,
-    },
     { /* NULL */ },
 };
 
diff --git a/qapi-schema.json b/qapi-schema.json
index 087a46305e..b2814cd510 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -659,6 +659,50 @@
 { 'command': 'query-spice', 'returns': 'SpiceInfo' }
 
 ##
+# @BalloonInfo:
+#
+# Information about the guest balloon device.
+#
+# @actual: the number of bytes the balloon currently contains
+#
+# @mem_swapped_in: #optional number of pages swapped in within the guest
+#
+# @mem_swapped_out: #optional number of pages swapped out within the guest
+#
+# @major_page_faults: #optional number of major page faults within the guest
+#
+# @minor_page_faults: #optional number of minor page faults within the guest
+#
+# @free_mem: #optional amount of memory (in bytes) free in the guest
+#
+# @total_mem: #optional amount of memory (in bytes) visible to the guest
+#
+# Since: 0.14.0
+#
+# Notes: all current versions of QEMU do not fill out optional information in
+#        this structure.
+##
+{ 'type': 'BalloonInfo',
+  'data': {'actual': 'int', '*mem_swapped_in': 'int',
+           '*mem_swapped_out': 'int', '*major_page_faults': 'int',
+           '*minor_page_faults': 'int', '*free_mem': 'int',
+           '*total_mem': 'int'} }
+
+##
+# @query-balloon:
+#
+# Return information about the balloon device.
+#
+# Returns: @BalloonInfo on success
+#          If the balloon driver is enabled but not functional because the KVM
+#          kernel module cannot support it, KvmMissingCap
+#          If no balloon device is present, DeviceNotActive
+#
+# Since: 0.14.0
+##
+{ 'command': 'query-balloon', 'returns': 'BalloonInfo' }
+
+##
 # @quit:
 #
 # This command will cause the QEMU process to exit gracefully.  While every
diff --git a/qmp-commands.hx b/qmp-commands.hx
index e99c240f1a..8ef6ca276a 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1989,3 +1989,8 @@ Example:
 
 EQMP
 
+    {
+        .name       = "query-balloon",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_input_query_balloon,
+    },