Re: [Qemu-devel] [PATCH RFC v3 5/5] block: Crude initial implementation of -blockdev

[Eric Blake]

On 02/21/2017 03:01 PM, Markus Armbruster wrote:
> The new command line option -blockdev works like QMP command
> blockdev-add.
> 
> The option argument may be given in JSON syntax, exactly as in QMP.
> Example usage:
> 
>     -blockdev '{"node-name": "foo", "driver": "raw", "file": {"driver": 
> "file", "filename": "foo.img"} }'
> 
> The JSON argument doesn't exactly blend into the existing option
> syntax, so the traditional KEY=VALUE,... syntax is also supported,
> using dotted keys to do the nesting:
> 
>     -blockdev node-name=foo,driver=raw,file.driver=file,file.filename=foo.img

Some of the list ideas were allowing mix-and-match or re-opening the
dict; do we want to allow any of these? (maybe as followups?)

-blockdev
node-name=foo,driver=raw,file='{"driver":"file"}',file.filename=foo.img


> 
> Note that calling qmp_blockdev_add() (say via qmp_marshal_block_add())
> right away would crash.  We need to stash the configuration for later
> instead.  This is crudely done, and bypasses QemuOpts, even though
> storing configuration is what QemuOpts is for.  Need to revamp option
> infrastructure to support QAPI types like BlockdevOptions.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  qemu-options.hx |  3 +++
>  vl.c            | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 53 insertions(+)
> 
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9936cf3..36a38d7 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -512,6 +512,9 @@ Use @var{file} as CD-ROM image (you cannot use 
> @option{-hdc} and
>  using @file{/dev/cdrom} as filename (@pxref{host_drives}).
>  ETEXI
>  
> +DEF("blockdev", HAS_ARG, QEMU_OPTION_blockdev,
> +    "-blockdev FIXME document\n", QEMU_OPTION_blockdev)

Adequate for an RFC, but I can see how you want to improve it.

> @@ -3095,6 +3104,37 @@ int main(int argc, char **argv, char **envp)
>                  drive_add(IF_DEFAULT, popt->index - QEMU_OPTION_hda, optarg,
>                            HD_OPTS);
>                  break;
> +            case QEMU_OPTION_blockdev:
> +                {
> +                    BlockdevOptions_queue *bdo = 
> g_new(BlockdevOptions_queue, 1);
> +                    bool is_json = optarg[0] == '{';
> +                    QObject *obj;
> +                    QDict *args;
> +                    Visitor *v;
> +
> +                    if (is_json) {
> +                        obj = qobject_from_json(optarg);
> +                        // TODO get error out of parser

Yeah, that's something we still need to improve.

> +                        if (!obj) {
> +                            error_report("invalid JSON");
> +                            exit(1);
> +                        }
> +                        args = qobject_to_qdict(obj);
> +                        assert(args);
> +                        v = qobject_input_visitor_new(QOBJECT(args), true);
> +                    } else {
> +                        args = keyval_parse(optarg, "driver", &error_fatal);
> +                        v = 
> qobject_input_visitor_new_autocast(QOBJECT(args));
> +                    }

Pretty slick!  And answers my question: no mix-and-match of JSON and
dotted (all one or the other) within a single -blockdev argument.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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