Re: [PATCH v15 18/23] accel: introduce AccelCPUClass extending CPUClass

[Claudio Fontana <cfontana@suse.de>]

On 2/3/21 3:27 PM, Philippe Mathieu-Daudé wrote:
> On 2/1/21 11:08 AM, Claudio Fontana wrote:
>> add a new optional interface to CPUClass, which allows accelerators
>> to extend the CPUClass with additional accelerator-specific
>> initializations.
>>
>> Signed-off-by: Claudio Fontana <cfontana@suse.de>
>> ---
>>  include/hw/core/accel-cpu.h | 35 +++++++++++++++++++++++++++++
>>  include/hw/core/cpu.h       |  1 +
>>  accel/accel-common.c        | 44 +++++++++++++++++++++++++++++++++++++
>>  MAINTAINERS                 |  1 +
>>  4 files changed, 81 insertions(+)
>>  create mode 100644 include/hw/core/accel-cpu.h
>>
>> diff --git a/include/hw/core/accel-cpu.h b/include/hw/core/accel-cpu.h
>> new file mode 100644
>> index 0000000000..c7c137dc9a
>> --- /dev/null
>> +++ b/include/hw/core/accel-cpu.h
>> @@ -0,0 +1,35 @@
>> +/*
>> + * Accelerator interface, specializes CPUClass
>> + *
>> + * Copyright 2021 SUSE LLC
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
>> + * See the COPYING file in the top-level directory.
>> + */
>> +
>> +#ifndef ACCEL_CPU_H
>> +#define ACCEL_CPU_H
>> +
>> +/*
>> + * these defines cannot be in cpu.h, because we are using
>> + * CPU_RESOLVING_TYPE here.
>> + * Use this header to define your accelerator-specific
>> + * cpu-specific accelerator interfaces.
>> + */
>> +
>> +#define TYPE_ACCEL_CPU "accel-" CPU_RESOLVING_TYPE
>> +#define ACCEL_CPU_NAME(name) (name "-" TYPE_ACCEL_CPU)
>> +typedef struct AccelCPUClass AccelCPUClass;
>> +DECLARE_CLASS_CHECKERS(AccelCPUClass, ACCEL_CPU, TYPE_ACCEL_CPU)
>> +
>> +typedef struct AccelCPUClass {
>> +    /*< private >*/
>> +    ObjectClass parent_class;
>> +    /*< public >*/
>> +
>> +    void (*cpu_class_init)(CPUClass *cc);
>> +    void (*cpu_instance_init)(CPUState *cpu);
>> +    void (*cpu_realizefn)(CPUState *cpu, Error **errp);
>> +} AccelCPUClass;
> 
> This header only makes sense if you forward-declare CPUClass
> in "qemu/typedefs.h", so accelerators don't have to include
> "hw/core/cpu.h".
> 

Can you clarify what you mean? I don't see how it follows that this header only makes sense if I forward-declare CPUClass.

This is necessary for the accel-specific target-specific code that needs to extend cpu classes with Accel CPU interfaces,
in this series f.e.:

target/i386/kvm/kvm-cpu.c
target/i386/hvf/hvf-cpu.c
target/i386/tcg/tcg-cpu.c

Ciao,

Claudio