Re: [Qemu-devel] [PATCH v3 1/4] target-arm: Add CPU property to disable AArch64

[Peter Maydell]

On 3 February 2015 at 19:14, Peter Maydell <address@hidden> wrote:
> On 27 January 2015 at 23:58, Greg Bellows <address@hidden> wrote:
>>  static void aarch64_cpu_initfn(Object *obj)
>>  {
>> +    object_property_add_bool(obj, "aarch64", aarch64_cpu_get_aarch64,
>> +                             aarch64_cpu_set_aarch64, NULL);
>> +    object_property_set_description(obj, "aarch64",
>> +                                    "Set on/off to enable/disable aarch64 "
>> +                                    "execution state ",
>> +                                    NULL);
>>  }
>
> This all looks OK code-wise. Still need to think about whether we
> can manage to end up with a nicer interface to the user than
> cpuname,-aarch64, though.

[I meant "-cpu cpuname,aarch64=off", hadn't processed that we've
updated to the new style syntax.]

I had a think about this as I was cycling home, and I (re)convinced
myself that modelling this as "remove the AArch64 feature flag" is
the right way to do it, which then just leaves us with "what's the
best user-facing UI we can manage to expose that?".

Suppose that we had two properties/feature flag switches that do
the same thing but have inverse sense:

  aarch64=off
  aarch32-only=on

Would that help, or just be more confusing?

-- PMM