[RFC v4 4/6] qmp: add QMP command x-debug-virtio-queue-status

[Laurent Vivier <lvivier@redhat.com>]

This new command shows internal status of a VirtQueue.
(vrings and indexes).

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 hw/virtio/virtio-stub.c |  6 +++
 hw/virtio/virtio.c      | 35 +++++++++++++++
 qapi/virtio.json        | 98 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 139 insertions(+)

diff --git a/hw/virtio/virtio-stub.c b/hw/virtio/virtio-stub.c
index ddb592f72eee..3c1bf172acf6 100644
--- a/hw/virtio/virtio-stub.c
+++ b/hw/virtio/virtio-stub.c
@@ -17,3 +17,9 @@ VirtioStatus *qmp_x_debug_virtio_status(const char* path, Error **errp)
 {
     return qmp_virtio_unsupported(errp);
 }
+
+VirtQueueStatus *qmp_x_debug_virtio_queue_status(const char *path,
+                                                 uint16_t queue, Error **errp)
+{
+    return qmp_virtio_unsupported(errp);
+}
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 59bf6ef651a6..57552bf05014 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3877,6 +3877,41 @@ static VirtIODevice *virtio_device_find(const char *path)
     return NULL;
 }
 
+VirtQueueStatus *qmp_x_debug_virtio_queue_status(const char *path,
+                                                 uint16_t queue, Error **errp)
+{
+    VirtIODevice *vdev;
+    VirtQueueStatus *status;
+
+    vdev = virtio_device_find(path);
+    if (vdev == NULL) {
+        error_setg(errp, "Path %s is not a VirtIO device", path);
+        return NULL;
+    }
+
+    if (queue >= VIRTIO_QUEUE_MAX || !virtio_queue_get_num(vdev, queue)) {
+        error_setg(errp, "Invalid virtqueue number %d", queue);
+        return NULL;
+    }
+
+    status = g_new0(VirtQueueStatus, 1);
+    status->queue_index = vdev->vq[queue].queue_index;
+    status->inuse = vdev->vq[queue].inuse;
+    status->vring_num = vdev->vq[queue].vring.num;
+    status->vring_num_default = vdev->vq[queue].vring.num_default;
+    status->vring_align = vdev->vq[queue].vring.align;
+    status->vring_desc = vdev->vq[queue].vring.desc;
+    status->vring_avail = vdev->vq[queue].vring.avail;
+    status->vring_used = vdev->vq[queue].vring.used;
+    status->last_avail_idx = vdev->vq[queue].last_avail_idx;
+    status->shadow_avail_idx = vdev->vq[queue].shadow_avail_idx;
+    status->used_idx = vdev->vq[queue].used_idx;
+    status->signalled_used = vdev->vq[queue].signalled_used;
+    status->signalled_used_valid = vdev->vq[queue].signalled_used_valid;
+
+    return status;
+}
+
 #define CONVERT_FEATURES(type, map)                \
     ({                                           \
         type *list = NULL;                         \
diff --git a/qapi/virtio.json b/qapi/virtio.json
index 69dd107d0c9b..43c234a9fc69 100644
--- a/qapi/virtio.json
+++ b/qapi/virtio.json
@@ -308,3 +308,101 @@
   'data': { 'path': 'str' },
   'returns': 'VirtioStatus'
 }
+
+##
+# @VirtQueueStatus:
+#
+# Status of a VirtQueue
+#
+# @queue-index: VirtQueue queue_index
+#
+# @inuse: VirtQueue inuse
+#
+# @vring-num: VirtQueue vring.num
+#
+# @vring-num-default: VirtQueue vring.num_default
+#
+# @vring-align: VirtQueue vring.align
+#
+# @vring-desc: VirtQueue vring.desc
+#
+# @vring-avail: VirtQueue vring.avail
+#
+# @vring-used: VirtQueue vring.used
+#
+# @last-avail-idx: VirtQueue last_avail_idx
+#
+# @shadow-avail-idx: VirtQueue shadow_avail_idx
+#
+# @used-idx: VirtQueue used_idx
+#
+# @signalled-used: VirtQueue signalled_used
+#
+# @signalled-used-valid: VirtQueue signalled_used_valid
+#
+# Since: 5.1
+#
+##
+
+{ 'struct': 'VirtQueueStatus',
+  'data': {
+    'queue-index': 'uint16',
+    'inuse': 'uint32',
+    'vring-num': 'int',
+    'vring-num-default': 'int',
+    'vring-align': 'int',
+    'vring-desc': 'uint64',
+    'vring-avail': 'uint64',
+    'vring-used': 'uint64',
+    'last-avail-idx': 'uint16',
+    'shadow-avail-idx': 'uint16',
+    'used-idx': 'uint16',
+    'signalled-used': 'uint16',
+    'signalled-used-valid': 'uint16'
+  }
+}
+
+##
+# @x-debug-virtio-queue-status:
+#
+# Return the status of a given VirtQueue
+#
+# @path: QOBject path of the VirtIODevice
+#
+# @queue: queue number to examine
+#
+# Returns: Status of the VirtQueue
+#
+# Since: 5.1
+#
+# Example:
+#
+# -> { "execute": "x-debug-virtio-queue-status",
+#      "arguments": {
+#          "path": "/machine/peripheral-anon/device[3]/virtio-backend",
+#          "queue": 0
+#      }
+#   }
+# <- { "return": {
+#      "signalled-used": 373,
+#      "inuse": 0,
+#      "vring-desc": 864411648,
+#      "vring-num-default": 256,
+#      "signalled-used-valid": 1,
+#      "vring-avail": 864415744,
+#      "last-avail-idx": 373,
+#      "queue-index": 0,
+#      "vring-used": 864416320,
+#      "shadow-avail-idx": 619,
+#      "used-idx": 373,
+#      "vring-num": 256,
+#      "vring-align": 4096
+#      }
+#    }
+#
+##
+
+{ 'command': 'x-debug-virtio-queue-status',
+  'data': { 'path': 'str', 'queue': 'uint16' },
+  'returns': 'VirtQueueStatus'
+}
-- 
2.26.2