Re: [Qemu-devel] [PATCH V4] vl.c: fixed regression in machine error message

[Eduardo Habkost <ehabkost@redhat.com>]

On Mon, Feb 08, 2016 at 01:54:29PM +0200, Marcel Apfelbaum wrote:
> Commit e1ce0c3cb(vl.c: fix regression when reading machine type from config file)
> fixed the error message when the machine type was supplied inside the
> config file. However now the option name is not displayed correctly if
> the error happens when the machine is specified at command line.
> 
> Running
>     ./x86_64-softmmu/qemu-system-x86_64 -M q35-1.5 -redir tcp:8022::22
> will result in the error message:
>     qemu-system-x86_64: -redir tcp:8022::22: unsupported machine type
>     Use -machine help to list supported machines
> 
> Fixed it by restoring the error location and also extracted the code
> dealing with machine options into a separate function.
> 
> Reported-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> ---
> 
> v3 -> v4:
>    - removed double call of loc_push_none (thanks again Laszlo)
> 
> v2 -> v3:
>  - fixed commit message and called qemu_get_machine_opts only once. (thanks Laszlo)
> 
> v1 -> v2:
>  - Addressed Laszlo Ersek's comments:
>    - no need to save the machine options location, is saved in opts
>    - rename the extracted method to set_machine_options
>    - added the bug reporter to the CC
>  
>  - tested with and without the config file and the error message is now OK:
>  config file:
>     - qemu-system-x86_64:machine-bug.conf:3: unsupported machine type
>  cli:
>    - qemu-system-x86_64: -M q35-1.5: unsupported machine type
> 
> Thanks,
> Marcel
> 
>  vl.c | 38 +++++++++++++++++++++++++++-----------
>  1 file changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/vl.c b/vl.c
> index 2c03f54..5e22a35 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2748,6 +2748,31 @@ static const QEMUOption *lookup_opt(int argc, char **argv,
>      return popt;
>  }
>  
> +static void set_machine_options(MachineClass **machine_class)
> +{
> +    const char *optarg;
> +    QemuOpts *opts;
> +    Location loc;
> +
> +    loc_push_none(&loc);
> +
> +    opts = qemu_get_machine_opts();
> +    qemu_opts_loc_restore(opts);
> +
> +    optarg = qemu_opt_get(opts, "type");
> +    if (optarg) {
> +        *machine_class = machine_parse(optarg);
> +    }
> +
> +    if (*machine_class == NULL) {
> +        error_report("No machine specified, and there is no default");
> +        error_printf("Use -machine help to list supported machines\n");
> +        exit(1);
> +    }
> +
> +    loc_pop(&loc);
> +}
> +
>  static int machine_set_property(void *opaque,
>                                  const char *name, const char *value,
>                                  Error **errp)
> @@ -4028,17 +4053,7 @@ int main(int argc, char **argv, char **envp)
>  
>      replay_configure(icount_opts);
>  
> -    opts = qemu_get_machine_opts();
> -    optarg = qemu_opt_get(opts, "type");
> -    if (optarg) {
> -        machine_class = machine_parse(optarg);
> -    }
> -
> -    if (machine_class == NULL) {
> -        error_report("No machine specified, and there is no default");
> -        error_printf("Use -machine help to list supported machines\n");
> -        exit(1);
> -    }
> +    set_machine_options(&machine_class);
>  
>      set_memory_options(&ram_slots, &maxram_size, machine_class);
[Extra context for reference:]
> 
>    loc_set_none();

You are fixing the machine error message, but not the root cause:

  $ ./x86_64-softmmu/qemu-system-x86_64 -m size= -vnc :0
  qemu-system-x86_64: -vnc :0: missing 'size' option value
  $ ./x86_64-softmmu/qemu-system-x86_64 -icount rr=x -vnc :0
  qemu-system-x86_64: -vnc :0: Invalid icount rr option: x

Moving the loc_set_none() call above replay_configure() should fix the bug in
the three cases.

Setting location in set_machine_options(), set_memory_options(), and
replay_configure() would be nice, too. But I would prefer to apply a one-line
fix first, and then consider improving the machine/memory/icount error
messages.

-- 
Eduardo