Re: [RFC v4 9/9] i386: split cpu accelerators from cpu.c

[Claudio Fontana <cfontana@suse.de>]

On 11/20/20 6:44 PM, Eduardo Habkost wrote:
> On Fri, Nov 20, 2020 at 03:49:09PM +0100, Claudio Fontana wrote:
>> split cpu.c into:
>>
>> cpu.c            cpuid and common x86 cpu functionality
>> host-cpu.c       host x86 cpu functions and "host" cpu type
>> kvm/cpu.c        KVM x86 cpu type
>> hvf/cpu.c        HVF x86 cpu type
>> tcg/cpu.c        TCG x86 cpu type
>>
>> The link to the accel class is set in the X86CPUClass classes
>> at MODULE_INIT_ACCEL_CPU time, when the accelerator is known.
>>
>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
> [...]
>> +static void hvf_cpu_accel_class_init(ObjectClass *oc, void *data)
>> +{
>> +    X86CPUAccelClass *acc = X86_CPU_ACCEL_CLASS(oc);
>> +
>> +    acc->cpu_realizefn = host_cpu_realizefn;
>> +    acc->cpu_common_class_init = hvf_cpu_common_class_init;
>> +    acc->cpu_instance_init = hvf_cpu_instance_init;
>> +};
>> +static const TypeInfo hvf_cpu_accel_type_info = {
>> +    .name = X86_CPU_ACCEL_TYPE_NAME("hvf"),
>> +
>> +    .parent = TYPE_X86_CPU_ACCEL,
>> +    .class_init = hvf_cpu_accel_class_init,
>> +};
>> +static void hvf_cpu_accel_register_types(void)
>> +{
>> +    type_register_static(&hvf_cpu_accel_type_info);
>> +}
>> +type_init(hvf_cpu_accel_register_types);
>> +
>> +static void hvf_cpu_accel_init(void)
>> +{
>> +    if (hvf_enabled()) {
>> +        x86_cpu_accel_init(X86_CPU_ACCEL_TYPE_NAME("hvf"));
>> +    }
>> +}
>> +
>> +accel_cpu_init(hvf_cpu_accel_init);
> 
> The point of my suggestion of using QOM is to not require
> separate accel_cpu_init() functions and (hvf|tcg|kvm)_enabled()
> checks.
> 
> If we still have separate accel_cpu_init() functions for calling
> x86_cpu_accel_init() with the right argument, using a pointer to
> static variables like &hvf_cpu_accel (like you did before) was
> simpler and required less boilerplate code.



Yes I agree.




> 
> However, the difference is that with the X86_CPU_ACCEL_TYPE_NAME
> macro + object_class_by_name(), you don't need the separate
> accel_cpu_init() functions for each accelerator.
> 
> All you need is a single:
> 
>   x86_cpu_accel_init(X86_CPU_ACCEL_TYPE_NAME(chosen_accel_name));
> 
> call somewhere in the initialization path.


Makes sense. The problem is just determining chosen_accel_name.


> 
> A good place for the x86_cpu_accel_init() call would be
> do_configure_accelerator(), but the function is arch-specific.
> That's why I suggested a cpu_accel_arch_init() function at
> https://lore.kernel.org/qemu-devel/20201118220750.GP1509407@habkost.net
> 


Fine by me. I'd use a specific init step for this, but that also works.

Ciao,

Clauidio