Re: [Qemu-devel] [PATCH v4 07/28] qmp: Clean up how we enforce capability negotiation

[Eric Blake]

On 03/03/2017 06:32 AM, Markus Armbruster wrote:
> To enforce capability negotiation before normal operation,
> handle_qmp_command() inspects every command before it's handed off to
> qmp_dispatch().  This is a bit of a layering violation, and results in
> duplicated code.
> 
> Before capability negotiation (!cur_mon->in_command_mode), we fail
> commands other than "qmp_capabilities".  This is what enforces
> capability negotiation.
> 
> Afterwards, we fail command "qmp_capabilities".
> 
> Clean this up as follows.
> 
> The obvious place to fail a command is the command itself, so move the
> "afterwards" check to qmp_qmp_capabilities().
> 
> We do the "before" check in every other command, but that would be
> bothersome.  Instead, start with an alternate list of commant that

s/commant/commands/

> contains only "qmp_capabilities".  Switch to the full list in
> qmp_qmp_capabilities().
> 
> Additionally, replace the generic human-readable error message for
> CommandNotFound by one that reminds the user to run qmp_capabilities.
> Without that, we'd regress commit 2d5a834.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  monitor.c | 76 
> +++++++++++++++++++++++++++++++++++----------------------------
>  1 file changed, 42 insertions(+), 34 deletions(-)
> 

> @@ -3786,11 +3785,20 @@ static void handle_qmp_command(JSONMessageParser 
> *parser, GQueue *tokens)
>      cmd_name = qdict_get_str(qdict, "execute");
>      trace_handle_qmp_command(mon, cmd_name);
>  
> -    if (invalid_qmp_mode(mon, cmd_name, &err)) {
> -        goto err_out;
> -    }
> +    rsp = qmp_dispatch(cur_mon->qmp.commands, req);
>  
> -    rsp = qmp_dispatch(&qmp_commands, req);
> +    qdict = qdict_get_qdict(qobject_to_qdict(rsp), "error");
> +    if (qdict) {
> +        if (mon->qmp.commands == &qmp_cap_negotiation_commands
> +            && !g_strcmp0(qdict_get_try_str(qdict, "class"),
> +                    QapiErrorClass_lookup[ERROR_CLASS_COMMAND_NOT_FOUND])) {

Could join these two 'if' into one, for less {}, but that's cosmetic.

Reviewed-by: Eric Blake <address@hidden>

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

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