[PATCH 4/4] qapi: introduce CONFIG_READ event

[Vladimir Sementsov-Ogievskiy]

Send a new event when guest reads virtio-pci config after
virtio_notify_config() call.

That's useful to check that guest fetched modified config, for example
after resizing disk backend.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru>
---
 hw/virtio/virtio-pci.c |  9 +++++++++
 include/monitor/qdev.h |  1 +
 monitor/monitor.c      |  1 +
 qapi/qdev.json         | 22 ++++++++++++++++++++++
 softmmu/qdev-monitor.c |  5 +++++
 5 files changed, 38 insertions(+)

diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index dd4620462b..f24f8ff03d 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -23,6 +23,7 @@
 #include "hw/boards.h"
 #include "hw/virtio/virtio.h"
 #include "migration/qemu-file-types.h"
+#include "monitor/qdev.h"
 #include "hw/pci/pci.h"
 #include "hw/pci/pci_bus.h"
 #include "hw/qdev-properties.h"
@@ -541,6 +542,10 @@ static uint64_t virtio_pci_config_read(void *opaque, 
hwaddr addr,
     }
     addr -= config;
 
+    if (vdev->generation > 0) {
+        qdev_config_read_event(DEVICE(proxy));
+    }
+
     switch (size) {
     case 1:
         val = virtio_config_readb(vdev, addr);
@@ -1728,6 +1733,10 @@ static uint64_t virtio_pci_device_read(void *opaque, 
hwaddr addr,
         return UINT64_MAX;
     }
 
+    if (vdev->generation > 0) {
+        qdev_config_read_event(DEVICE(proxy));
+    }
+
     switch (size) {
     case 1:
         val = virtio_config_modern_readb(vdev, addr);
diff --git a/include/monitor/qdev.h b/include/monitor/qdev.h
index 949a3672cb..f0b0eab07e 100644
--- a/include/monitor/qdev.h
+++ b/include/monitor/qdev.h
@@ -39,6 +39,7 @@ DeviceState *qdev_device_add_from_qdict(const QDict *opts,
 const char *qdev_set_id(DeviceState *dev, char *id, Error **errp);
 
 void qdev_hotplug_device_on_event(DeviceState *dev);
+void qdev_config_read_event(DeviceState *dev);
 
 DeviceAndPath *qdev_new_device_and_path(DeviceState *dev);
 
diff --git a/monitor/monitor.c b/monitor/monitor.c
index 941f87815a..f8aa91b190 100644
--- a/monitor/monitor.c
+++ b/monitor/monitor.c
@@ -315,6 +315,7 @@ static MonitorQAPIEventConf 
monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
     [QAPI_EVENT_QUORUM_FAILURE]    = { 1000 * SCALE_MS },
     [QAPI_EVENT_VSERPORT_CHANGE]   = { 1000 * SCALE_MS },
     [QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE] = { 1000 * SCALE_MS },
+    [QAPI_EVENT_X_CONFIG_READ]   = { 300 * SCALE_MS },
 };
 
 /*
diff --git a/qapi/qdev.json b/qapi/qdev.json
index 2468f8bddf..37a8785b81 100644
--- a/qapi/qdev.json
+++ b/qapi/qdev.json
@@ -329,3 +329,25 @@
 # Since: 8.2
 ##
 { 'command': 'x-device-sync-config', 'data': {'id': 'str'} }
+
+##
+# @X_CONFIG_READ:
+#
+# Emitted whenever guest reads virtio device config after config change.
+#
+# @device: device name
+#
+# @path: device path
+#
+# Since: 5.0.1-24
+#
+# Example:
+#
+# <- { "event": "X_CONFIG_READ",
+#      "data": { "device": "virtio-net-pci-0",
+#                "path": "/machine/peripheral/virtio-net-pci-0" },
+#      "timestamp": { "seconds": 1265044230, "microseconds": 450486 } }
+#
+##
+{ 'event': 'X_CONFIG_READ',
+  'data': { '*device': 'str', 'path': 'str' } }
diff --git a/softmmu/qdev-monitor.c b/softmmu/qdev-monitor.c
index b485375049..d0f022e925 100644
--- a/softmmu/qdev-monitor.c
+++ b/softmmu/qdev-monitor.c
@@ -1252,3 +1252,8 @@ void qdev_hotplug_device_on_event(DeviceState *dev)
     dev->device_on_event_sent = true;
     qapi_event_send_x_device_on(dev->id, dev->canonical_path);
 }
+
+void qdev_config_read_event(DeviceState *dev)
+{
+    qapi_event_send_x_config_read(dev->id, dev->canonical_path);
+}
-- 
2.34.1