Re: [Qemu-devel] [PATCH 19/19] Add a -capabilities argument to allow easy query for static QEMU info

[Anthony Liguori <anthony@codemonkey.ws>]

On 06/07/2010 09:42 AM, Daniel P. Berrange wrote:
> The QMP monitor provides a number of commands for querying info about
> the QEMU binary capabilities. Given that these commands don't take
> any options and just return static data, requiring the use of QMP is
> unnecessarily onerous. This adds a new '-capabilities' command line
> argument as a syntactic sugar for accessing the QMP commands that
> just return static QEMU binary capabilities.
>
> Setting the '-capabilities' argument causes QEMU to output the requested
> data on stdout, pretty printed in JSON format. The argument expects an
> associated value to identify the data to be printed. This can be one of
> the strings version|machines|devices|cputypes|target|commands|argv|netdev
>
> To query all possible data at once, the shorthand 'all' is allowed.
>
> The output is a QDict where the key is the type of data requested, and
> the value is the JSON data from the associated monitor command. For
> example:
>    

I think the idea is good but I think we should use a different name as 
QMP capabilities has a different meaning.

Maybe features?

Regards,

Anthony Liguori

>    $ qemu -capabilities all
>    {
>      "machines": [
>          {
>              "name": "pc-0.13",
>              "description": "Standard PC",
>              "default": 0
>          },
>          {
>              "name": "pc",
>              ....
>          }
>          ....
>       }
>       "version": {
>          "qemu": {
>              "micro": 50,
>              "minor": 12,
>              "major": 0
>          },
>          "package": ""
>       },
>       "target": {
>          "arch": "i386",
>          "wordsize": 32,
>       ...
>     }
>
> Signed-off-by: Daniel P. Berrange<berrange@redhat.com>
> ---
>   monitor.c       |    4 +-
>   monitor.h       |    2 +
>   qemu-options.hx |    9 +++++
>   vl.c            |  100 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   4 files changed, 113 insertions(+), 2 deletions(-)
>
> diff --git a/monitor.c b/monitor.c
> index 6203f75..401a27a 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -711,7 +711,7 @@ static void do_info_version_print(Monitor *mon, const QObject *data)
>    *
>    * { qemu: { "major": 0, "minor": 11, "micro": 5 }, "package": "" }
>    */
> -static void do_info_version(Monitor *mon, QObject **ret_data)
> +void do_info_version(Monitor *mon, QObject **ret_data)
>   {
>       const char *version = QEMU_VERSION;
>       int major = 0, minor = 0, micro = 0;
> @@ -760,7 +760,7 @@ static QObject *get_cmd_dict(const char *name)
>       return qobject_from_jsonf("{ 'name': %s }", p);
>   }
>
> -static void do_info_commands(Monitor *mon, QObject **ret_data)
> +void do_info_commands(Monitor *mon, QObject **ret_data)
>   {
>       QList *cmd_list;
>       const mon_cmd_t *cmd;
> diff --git a/monitor.h b/monitor.h
> index 733485f..dc376af 100644
> --- a/monitor.h
> +++ b/monitor.h
> @@ -57,5 +57,7 @@ typedef void (MonitorCompletion)(void *opaque, QObject *ret_data);
>   void monitor_set_error(Monitor *mon, QError *qerror);
>
>   void do_info_argv(Monitor *mon, QObject **data);
> +void do_info_version(Monitor *mon, QObject **ret_data);
> +void do_info_commands(Monitor *mon, QObject **ret_data);
>
>   #endif /* !MONITOR_H */
> diff --git a/qemu-options.hx b/qemu-options.hx
> index a6928b7..5f82347 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -27,6 +27,15 @@ STEXI
>   Display version information and exit
>   ETEXI
>
> +DEF("capabilities", HAS_ARG, QEMU_OPTION_capabilities,
> +    "-capabilities   all|version|machines|devices|cputypes|target|commands|argv|netdev\n"
> +    "                display capabilities of the QEMU binary and exit\n", QEMU_ARCH_ALL)
> +STEXI
> +@item -capabilities  all|version|machines|devices|cputypes|target|commands|argv|netdev
> +@findex -capabilities
> +Display capabilities of the QEMU binary and exit
> +ETEXI
> +
>   DEF("M", HAS_ARG, QEMU_OPTION_M,
>       "-M machine      select emulated machine (-M ? for list)\n", QEMU_ARCH_ALL)
>   STEXI
> diff --git a/vl.c b/vl.c
> index de010cc..1f165a1 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1988,6 +1988,97 @@ static void version(void)
>   }
>
>
> +enum {
> +    QEMU_CAPS_VERSION,
> +    QEMU_CAPS_MACHINES,
> +    QEMU_CAPS_DEVICES,
> +    QEMU_CAPS_CPUTYPES,
> +    QEMU_CAPS_TARGET,
> +    QEMU_CAPS_COMMANDS,
> +    QEMU_CAPS_ARGV,
> +    QEMU_CAPS_NETDEV,
> +    QEMU_CAPS_CONFIG,
> +
> +    QEMU_CAPS_LAST
> +};
> +
> +QEMU_ENUM_DECL(qemu_caps_flag);
> +QEMU_ENUM_IMPL(qemu_caps_flag, QEMU_CAPS_LAST,
> +               "version",
> +               "machines",
> +               "devices",
> +               "cputypes",
> +               "target",
> +               "commands",
> +               "argv",
> +               "netdev",
> +               "config");
> +
> +static int qemu_caps_flags_from_string(const char *flagsstr)
> +{
> +    if (strcmp(flagsstr, "all") == 0)
> +        return ~0;
> +    else {
> +        int i = qemu_caps_flag_from_string(flagsstr);
> +        if (i<  0)
> +            return 0;
> +        return (1<<  i);
> +    }
> +
> +    return 0;
> +}
> +typedef void (*qemu_caps_handler)(Monitor *mon, QObject **);
> +
> +/* Binding capabilities to a subset of monitor commands.
> + * The commands must only use static binary state, no
> + * VM runtime state and must accept mon=NULL
> + */
> +static const qemu_caps_handler qemu_caps_handlers[] = {
> +    do_info_version,
> +    do_info_machines,
> +    do_info_devices,
> +    do_info_cpu_types,
> +    do_info_target,
> +    do_info_commands,
> +    do_info_argv,
> +    do_info_netdev,
> +    do_info_config,
> +};
> +verify(ARRAY_SIZE(qemu_caps_handlers) == QEMU_CAPS_LAST);
> +
> +static void qemu_show_caps(const char *flagsstr)
> +{
> +    QDict *data = qdict_new();
> +    QString *json;
> +    int i;
> +    int flags;
> +
> +    flags = qemu_caps_flags_from_string(flagsstr);
> +    if (flags == 0) {
> +        fprintf(stderr, "Unknown capabilities '%s'\n", flagsstr);
> +        exit(1);
> +    }
> +
> +    for (i = 0 ; i<  QEMU_CAPS_LAST ; i++) {
> +        if (flags&  (1<<  i)) {
> +            QObject *val;
> +            qemu_caps_handler handler = qemu_caps_handlers[i];
> +            const char *name = qemu_caps_flag_to_string(i);
> +            (*handler)(NULL,&val);
> +            qdict_put_obj(data, name, val);
> +        }
> +    }
> +    json = qobject_to_json_pretty(QOBJECT(data));
> +    assert(json != NULL);
> +
> +    qstring_append_chr(json, '\n');
> +    fprintf(stdout, qstring_get_str(json));
> +
> +    QDECREF(json);
> +
> +}
> +
> +
>   /**
>    * do_info_argv():
>    *
> @@ -2647,6 +2738,7 @@ int main(int argc, char **argv, char **envp)
>   #endif
>       int show_vnc_port = 0;
>       int defconfig = 1;
> +    const char *showcaps = NULL;
>
>       error_set_progname(argv[0]);
>
> @@ -3020,6 +3112,9 @@ int main(int argc, char **argv, char **envp)
>                   version();
>                   exit(0);
>                   break;
> +            case QEMU_OPTION_capabilities:
> +                showcaps = optarg;
> +                break;
>               case QEMU_OPTION_m: {
>                   uint64_t value;
>                   char *ptr;
> @@ -3785,6 +3880,11 @@ int main(int argc, char **argv, char **envp)
>       if (qemu_opts_foreach(&qemu_device_opts, device_help_func, NULL, 0) != 0)
>           exit(0);
>
> +    if (showcaps) {
> +        qemu_show_caps(showcaps);
> +        exit(0);
> +    }
> +
>       if (watchdog) {
>           i = select_watchdog(watchdog);
>           if (i>  0)
>