[Qemu-devel] [PATCH v4] monitor: allow device_del to accept QOM paths

["Daniel P. Berrange" <berrange@redhat.com>]

Currently device_del requires that the client provide the
device short ID. device_add allows devices may be created
without giving an ID, at which point there is no way to
delete them with device_del. The QOM object path, however,
provides an alternative way to identify the devices.

Allowing device_del to accept an object path ensures all
devices are deletable regardless of whether they have an
ID.

 (qemu) device_add usb-mouse
 (qemu) qom-list /machine/peripheral-anon
 device[0] (child<usb-mouse>)
 type (string)
 (qemu) device_del /machine/peripheral-anon/device[0]

Devices are required to be marked as hotpluggable
otherwise an error is raised

 (qemu) device_del /machine/unattached/device[4]
 Device 'PIIX3' does not support hotplugging

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---

Changes in v4:

 - Drop additions to object_del, since that can be misused
   to delete internally created devices, and object_create
   mandates an ID parameter.

 hmp-commands.hx  |  3 ++-
 qapi-schema.json |  2 +-
 qdev-monitor.c   | 19 ++++++++++++++-----
 qmp-commands.hx  |  7 ++++++-
 4 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 286dcc7..e56373b 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -676,7 +676,8 @@ ETEXI
 STEXI
 @item device_del @var{id}
 @findex device_del
-Remove device @var{id}.
+Remove device @var{id}. @var{id} may be a short ID
+or a QOM object path.
 ETEXI
 
     {
diff --git a/qapi-schema.json b/qapi-schema.json
index 67fef37..273a906 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1950,7 +1950,7 @@
 #
 # Remove a device from a guest
 #
-# @id: the name of the device
+# @id: the name or QOM path of the device
 #
 # Returns: Nothing on success
 #          If @id is not a valid device, DeviceNotFound
diff --git a/qdev-monitor.c b/qdev-monitor.c
index f9e2d62..295441b 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -785,19 +785,28 @@ void qmp_device_add(QDict *qdict, QObject **ret_data, Error **errp)
 void qmp_device_del(const char *id, Error **errp)
 {
     Object *obj;
-    char *root_path = object_get_canonical_path(qdev_get_peripheral());
-    char *path = g_strdup_printf("%s/%s", root_path, id);
 
-    g_free(root_path);
-    obj = object_resolve_path_type(path, TYPE_DEVICE, NULL);
-    g_free(path);
+    if (id[0] == '/') {
+        obj = object_resolve_path(id, NULL);
+    } else {
+        char *root_path = object_get_canonical_path(qdev_get_peripheral());
+        char *path = g_strdup_printf("%s/%s", root_path, id);
 
+        g_free(root_path);
+        obj = object_resolve_path_type(path, TYPE_DEVICE, NULL);
+        g_free(path);
+    }
     if (!obj) {
         error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
                   "Device '%s' not found", id);
         return;
     }
 
+    if (!object_dynamic_cast(obj, TYPE_DEVICE)) {
+        error_setg(errp, "%s is not a hotpluggable device", id);
+        return;
+    }
+
     qdev_unplug(DEVICE(obj), errp);
 }
 
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 9848fd8..d3b4c7f 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -321,13 +321,18 @@ Remove a device.
 
 Arguments:
 
-- "id": the device's ID (json-string)
+- "id": the device's ID or QOM path (json-string)
 
 Example:
 
 -> { "execute": "device_del", "arguments": { "id": "net1" } }
 <- { "return": {} }
 
+Example:
+
+-> { "execute": "device_del", "arguments": { "id": "/machine/peripheral-anon/device[0]" } }
+<- { "return": {} }
+
 EQMP
 
     {
-- 
2.4.3