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

[Laszlo Ersek <lersek@redhat.com>]

On 02/07/16 17:24, 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 saving the error location and also extracted the code
> dealing with machine options into a separate function.
> 
> Reported-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> ---
> 
> Hi,
> 
> I hope I used "location" correctly, if anyone is aware of a simpler
> approach please advice.
> 
> Thanks,
> Marcel
> 
>  vl.c | 34 +++++++++++++++++++++++-----------
>  1 file changed, 23 insertions(+), 11 deletions(-)
> 
> diff --git a/vl.c b/vl.c
> index f043009..f8a9213 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2751,6 +2751,26 @@ static const QEMUOption *lookup_opt(int argc, char **argv,
>      return popt;
>  }
>  
> +static void machine_set_options(Location *machine_opt_loc,
> +                                MachineClass **machine_class)
> +{
> +    const char *optarg;
> +    Location *curr = loc_push_restore(machine_opt_loc);
> +
> +    optarg = qemu_opt_get(qemu_get_machine_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(curr);
> +}
> +
>  static int machine_set_property(void *opaque,
>                                  const char *name, const char *value,
>                                  Error **errp)
> @@ -2975,6 +2995,7 @@ int main(int argc, char **argv, char **envp)
>      const char *optarg;
>      const char *loadvm = NULL;
>      MachineClass *machine_class;
> +    Location machine_opt_loc = {0};
>      const char *cpu_model;
>      const char *vga_model = NULL;
>      const char *qtest_chrdev = NULL;
> @@ -3671,6 +3692,7 @@ int main(int argc, char **argv, char **envp)
>                  break;
>              case QEMU_OPTION_M:
>              case QEMU_OPTION_machine:
> +                loc_save(&machine_opt_loc);
>                  olist = qemu_find_opts("machine");
>                  opts = qemu_opts_parse_noisily(olist, optarg, true);
>                  if (!opts) {
> @@ -4019,17 +4041,7 @@ 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);
> -    }
> +    machine_set_options(&machine_opt_loc, &machine_class);
>  
>      set_memory_options(&ram_slots, &maxram_size, machine_class);
>  
> 

Sorry, I sent my email before noticing yours (in the original thread,
"Re: [Qemu-devel] command line error handling broken?").

Looks good (extracting machine_set_options()), but I think you don't
need to save the location for the option separately; the location gets
saved in the option automatically. It can be restored with
qemu_opts_loc_restore(), however it doesn't combine push & restore, so a
none location should be pushed first.

Also, "set_machine_options" would match "set_memory_options" better,
just below.

Thanks
Laszlo