Re: [Qemu-devel] [PATCH 2/2] vl: Print CPU help after we've registered the CPU accelerators

[Eduardo Habkost]

On Tue, Jan 31, 2017 at 02:11:59PM +0100, Thomas Huth wrote:
> When running with KVM on POWER, we register some CPU types during
> the initialization function of the ppc64 KVM code (which unfortunately
> also can not be done via a type_init() like it is done on x86).

Can you elaborate why it can't be done via type_init()? If the
QOM type hierarchy depends on any runtime data unavailable at
type_init(), we should fix that.


>                                                                 So to
> be able to see these updates in the CPU help text, the code that calls
> list_cpus() has to be run after configure_accelerator(). This move should
> be fine since the "cpu_model" variable is also never used before the call
> to configure_accelerator(), and thus there should not be any unwanted
> side effects in the code before configure_accelerator() if the user
> started QEMU with "-cpu ?" or "-cpu help".
> 
> Signed-off-by: Thomas Huth <address@hidden>

I am not convinced that the output of "-cpu help" and
"-cpu help -machine accel=kvm" should look different. Do you have
an example of what exactly is wrong with the output currently?

I actually believe list_cpus() needs to be called _earlier_, not
later. Otherwise we won't be able to fix this bug:

  $ qemu-system-arm -cpu help
  qemu-system-arm:/usr/local/etc/qemu/qemu.conf:1: No machine specified, and 
there is no default
  Use -machine help to list supported machines
  $ 

> ---
>  vl.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/vl.c b/vl.c
> index 0b72b12..315c5c3 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -4055,11 +4055,6 @@ int main(int argc, char **argv, char **envp)
>          qemu_set_hw_version(machine_class->hw_version);
>      }
>  
> -    if (cpu_model && is_help_option(cpu_model)) {
> -        list_cpus(stdout, &fprintf, cpu_model);
> -        exit(0);
> -    }
> -
>      if (!trace_init_backends()) {
>          exit(1);
>      }
> @@ -4298,6 +4293,11 @@ int main(int argc, char **argv, char **envp)
>  
>      configure_accelerator(current_machine);
>  
> +    if (cpu_model && is_help_option(cpu_model)) {
> +        list_cpus(stdout, &fprintf, cpu_model);
> +        exit(0);
> +    }
> +
>      if (qtest_chrdev) {
>          qtest_init(qtest_chrdev, qtest_log, &error_fatal);
>      }
> -- 
> 1.8.3.1
> 
> 

-- 
Eduardo