Re: [PATCH v2 3/4] target/riscv: add 'static' attribute of query-cpu-definitions

[Richard Henderson <richard.henderson@linaro.org>]

On 4/10/23 09:52, Daniel Henrique Barboza wrote:
> 'static' is defined in the QMP doc as:
> 
> "whether a CPU definition is static and will not change depending on
> QEMU version, machine type, machine options and accelerator options. A
> static model is always migration-safe."
> 
> For RISC-V we'll consider all named CPUs as static since their
> extensions can't be changed by user input. Generic CPUs will be
> considered non-static.
> 
> We aren't ready to make the change for generic CPUs yet because we're
> using the same class init for every CPU. We'll deal with it next.
> 
> Signed-off-by: Daniel Henrique Barboza<dbarboza@ventanamicro.com>
> ---
>   target/riscv/cpu-qom.h        | 3 +++
>   target/riscv/cpu.c            | 6 ++++++
>   target/riscv/riscv-qmp-cmds.c | 2 ++
>   3 files changed, 11 insertions(+)

Is 'static = true' really what you want as default?
Perhaps 'dynamic = false' (considering zero initialization) would be better?
Do you want an attribute that can be changed at all?

You could plausibly implement this via class inheritance instead.
E.g.

static const TypeInfo dynamic_cpu_type_info = {
     .name = TYPE_RISCV_DYN_CPU,
     .parent = TYPE_RISCV_CPU,
     .abstract = true,
     ...
};

and then the dynamic cpus inherit from that.  Your dynamic attribute becomes 
object_dynamic_cast(OBJECT(cpu), TYPE_RISCV_DYN_CPU) != NULL.


r~