Re: [RFC PATCH 1/3] qom: Always register FW_CFG_DATA_GENERATOR_INTERFACE

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

On Mon, Oct 05, 2020 at 12:54:40PM +0200, Philippe Mathieu-Daudé wrote:
> While the FW_CFG_DATA_GENERATOR_INTERFACE is only consumed
> by a device only available using system-mode (fw_cfg), it is
> implemented by a crypto component (tls-cipher-suites) which
> is always available when crypto is used.
> 
> Commit 69699f3055 introduced the following error in the
> qemu-storage-daemon binary:
> 
>   $ echo -e \
>     '{"execute": "qmp_capabilities"}\r\n{"execute": "qom-list-types"}\r\n{"execute": "quit"}\r\n' \
>     | storage-daemon/qemu-storage-daemon --chardev stdio,id=qmp0  --monitor qmp0
>   {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 5}, "package": ""}, "capabilities": ["oob"]}}
>   {"return": {}}
>   missing interface 'fw_cfg-data-generator' for object 'tls-creds'
>   Aborted (core dumped)
> 
> Since QOM dependencies are resolved at runtime, this issue
> could not be triggered at linktime, and we don't have test
> running the qemu-storage-daemon binary.
> 
> Fix by always registering the QOM interface.
> 
> Reported-by: Kevin Wolf <kwolf@redhat.com>
> Fixes: 69699f3055 ("crypto/tls-cipher-suites: Produce fw_cfg consumable blob")
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
> I first used:
> 
> +if config_host.has_key('CONFIG_GNUTLS') or have_system
> +  qom_ss.add(files('fw_cfg_interface.c'))
> +endif
> 
> but then realized anything could implement a QOM interface,
> so better keep this generic.
> ---
>  hw/nvram/fw_cfg.c      |  7 -------
>  qom/fw_cfg_interface.c | 15 +++++++++++++++

I feel this should be left in hw/nvram, but still added to qom_ss.

The code location should reflect the functional area and maintainership,
so we shouldn't move code just to satisfy linkage problems.

>  MAINTAINERS            |  1 +
>  qom/meson.build        |  5 +++++
>  4 files changed, 21 insertions(+), 7 deletions(-)
>  create mode 100644 qom/fw_cfg_interface.c
> 
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 0e95d057fd..08539a1aab 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -1360,18 +1360,11 @@ static const TypeInfo fw_cfg_mem_info = {
>      .class_init    = fw_cfg_mem_class_init,
>  };
>  
> -static const TypeInfo fw_cfg_data_generator_interface_info = {
> -    .parent = TYPE_INTERFACE,
> -    .name = TYPE_FW_CFG_DATA_GENERATOR_INTERFACE,
> -    .class_size = sizeof(FWCfgDataGeneratorClass),
> -};
> -
>  static void fw_cfg_register_types(void)
>  {
>      type_register_static(&fw_cfg_info);
>      type_register_static(&fw_cfg_io_info);
>      type_register_static(&fw_cfg_mem_info);
> -    type_register_static(&fw_cfg_data_generator_interface_info);
>  }
>  
>  type_init(fw_cfg_register_types)
> diff --git a/qom/fw_cfg_interface.c b/qom/fw_cfg_interface.c
> new file mode 100644
> index 0000000000..2b19502ffe
> --- /dev/null
> +++ b/qom/fw_cfg_interface.c
> @@ -0,0 +1,15 @@
> +#include "qemu/osdep.h"
> +#include "hw/nvram/fw_cfg.h"
> +
> +static const TypeInfo fw_cfg_data_generator_interface_info = {
> +    .parent = TYPE_INTERFACE,
> +    .name = TYPE_FW_CFG_DATA_GENERATOR_INTERFACE,
> +    .class_size = sizeof(FWCfgDataGeneratorClass),
> +};
> +
> +static void fw_cfg_register_types(void)
> +{
> +    type_register_static(&fw_cfg_data_generator_interface_info);
> +}
> +
> +type_init(fw_cfg_register_types)
> diff --git a/MAINTAINERS b/MAINTAINERS
> index b76fb31861..9c89d54b41 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2055,6 +2055,7 @@ R: Gerd Hoffmann <kraxel@redhat.com>
>  S: Supported
>  F: docs/specs/fw_cfg.txt
>  F: hw/nvram/fw_cfg.c
> +F: qom/fw_cfg_interface.c
>  F: stubs/fw_cfg.c
>  F: include/hw/nvram/fw_cfg.h
>  F: include/standard-headers/linux/qemu_fw_cfg.h
> diff --git a/qom/meson.build b/qom/meson.build
> index a1cd03c82c..7335f8c8a2 100644
> --- a/qom/meson.build
> +++ b/qom/meson.build
> @@ -7,6 +7,11 @@ qom_ss.add(files(
>    'qom-qobject.c',
>  ))
>  
> +# interfaces any object might implement
> +qom_ss.add(files(
> +  'fw_cfg_interface.c',
> +))
> +
>  qmp_ss.add(files('qom-qmp-cmds.c'))
>  softmmu_ss.add(files('qom-hmp-cmds.c'))
>  
> -- 
> 2.26.2
> 

Regards,
Daniel
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