Re: [Qemu-devel] [PATCH v2] monitor: allow object_del & device_del to accept QOM paths

[Markus Armbruster]

Gah, missed your v2!  Sorry for the noise on v1.

Still copying Andreas and Paolo for QOM expertise.

"Daniel P. Berrange" <address@hidden> writes:

> Currently both object_del and device_del require that the
> client provide the object/device short ID. While user
> creatable objects require an ID to be provided at time of
> creation, qdev devices may be created without giving an
> ID. The only unique identifier they would then have is the
> QOM object path.
>
> 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]
>
> Although objects require an ID to be provided upfront,
> there may be cases where the client would prefer to
> use QOM paths when deleting.
>
> Signed-off-by: Daniel P. Berrange <address@hidden>

Thanks for tackling this, it's long overdue!

I believe it makes sense no matter what we do about device IDs (see
thread "Should we auto-generate IDs?").

> ---
>  hmp-commands.hx  |  6 ++++--
>  qapi-schema.json |  4 ++--
>  qdev-monitor.c   | 14 +++++++++-----
>  qmp-commands.hx  | 13 +++++++++++--
>  qmp.c            | 10 +++++++---
>  5 files changed, 33 insertions(+), 14 deletions(-)
>
> Changed in v2:
>
>  - Fix stupid typo in qmp-commands.hx
>  - Expand parameter docs in qapi-schema.json
>
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index d3b7932..c0c113d 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -675,7 +675,8 @@ 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
>  
>      {
> @@ -1279,7 +1280,8 @@ ETEXI
>  STEXI
>  @item object_del
>  @findex object_del
> -Destroy QOM object.
> +Destroy QOM object. @var{id} may be a short ID
> +or a QOM object path.
>  ETEXI
>  
>  #ifdef CONFIG_SLIRP
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 4342a08..bf9ef3a 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
> @@ -2121,7 +2121,7 @@
>  #
>  # Remove a QOM object.
>  #
> -# @id: the name of the QOM object to remove
> +# @id: the name or path of the QOM object to remove
>  #
>  # Returns: Nothing on success
>  #          Error if @id is not a valid id for a QOM object
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index f9e2d62..894b799 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -785,13 +785,17 @@ 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);
> +    }

Blank line deleted right here, could perhaps be fixed up on commit.

>      if (!obj) {
>          error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
>                    "Device '%s' not found", id);
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index ba630b1..09fc206 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
>  
>      {
> @@ -965,7 +970,7 @@ Remove QOM object.
>  
>  Arguments:
>  
> -- "id": the object's ID (json-string)
> +- "id": the object's ID or QOM path (json-string)
>  
>  Example:
>  
> @@ -973,6 +978,10 @@ Example:
>  <- { "return": {} }
>  
>  
> +-> { "execute": "object-del", "arguments": { "id": "/objects/hostmem1" } }
> +<- { "return": {} }
> +
> +
>  EQMP
>  
>  
> diff --git a/qmp.c b/qmp.c
> index 403805a..11e9f51 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -678,11 +678,15 @@ void qmp_object_add(QDict *qdict, QObject **ret, Error 
> **errp)
>  
>  void qmp_object_del(const char *id, Error **errp)
>  {
> -    Object *container;
>      Object *obj;
>  
> -    container = object_get_objects_root();
> -    obj = object_resolve_path_component(container, id);
> +    if (id[0] == '/') {
> +        obj = object_resolve_path(id, NULL);
> +    } else {
> +        Object *container;
> +        container = object_get_objects_root();
> +        obj = object_resolve_path_component(container, id);
> +    }
>      if (!obj) {
>          error_setg(errp, "object id not found");
>          return;

I'd keep container right where it is.  We generally prefer keeping
declarations at the beginning of the function body, at least for small
functions.  Could also be touched up on commit.

Reviewed-by: Markus Armbruster <address@hidden>

If neither Andreas nor Paolo objects, I'd be willing to take this
through my tree.