Re: [PATCH v6 12/12] target/riscv: deprecate the 'any' CPU type

[Alistair Francis]

On Thu, Jul 27, 2023 at 6:39 PM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> The 'any' CPU type was introduced in commit dc5bd18fa5725 ("RISC-V CPU
> Core Definition"), being around since the beginning. It's not an easy
> CPU to use: it's undocumented and its name doesn't tell users much about
> what the CPU is supposed to bring. 'git log' doesn't help us either in
> knowing what was the original design of this CPU type.
>
> The closest we have is a comment from Alistair [1] where he recalls from
> memory that the 'any' CPU is supposed to behave like the newly added
> 'max' CPU. He also suggested that the 'any' CPU should be removed.
>
> The default CPUs are rv32 and rv64, so removing the 'any' CPU will have
> impact only on users that might have a script that uses '-cpu any'.
> And those users are better off using the default CPUs or the new 'max'
> CPU.
>
> We would love to just remove the code and be done with it, but one does
> not simply remove a feature in QEMU. We'll put the CPU in quarantine
> first, letting users know that we have the intent of removing it in the
> future.
>
> [1] https://lists.gnu.org/archive/html/qemu-devel/2023-07/msg02891.html
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  docs/about/deprecated.rst | 12 ++++++++++++
>  target/riscv/cpu.c        |  5 +++++
>  2 files changed, 17 insertions(+)
>
> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
> index 02ea5a839f..68afa43fd0 100644
> --- a/docs/about/deprecated.rst
> +++ b/docs/about/deprecated.rst
> @@ -371,6 +371,18 @@ QEMU's ``vhost`` feature, which would eliminate the high 
> latency costs under
>  which the 9p ``proxy`` backend currently suffers. However as of to date 
> nobody
>  has indicated plans for such kind of reimplemention unfortunately.
>
> +RISC-V 'any' CPU type ``-cpu any`` (since 8.2)
> +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> +
> +The 'any' CPU type was introduced back in 2018 and has been around since the
> +initial RISC-V QEMU port. Its usage has always been unclear: users don't know
> +what to expect from a CPU called 'any', and in fact the CPU does not do 
> anything
> +special that aren't already done by the default CPUs rv32/rv64.
> +
> +After the introduction of the 'max' CPU type RISC-V now has a good coverage
> +of generic CPUs: rv32 and rv64 as default CPUs and 'max' as a feature 
> complete
> +CPU for both 32 and 64 bit builds. Users are then discouraged to use the 
> 'any'
> +CPU type starting in 8.2.
>
>  Block device options
>  ''''''''''''''''''''
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 3e840f1a20..b5a2266eef 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1477,6 +1477,11 @@ static void riscv_cpu_realize(DeviceState *dev, Error 
> **errp)
>      RISCVCPUClass *mcc = RISCV_CPU_GET_CLASS(dev);
>      Error *local_err = NULL;
>
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_RISCV_CPU_ANY) != NULL) {
> +        warn_report("The 'any' CPU is deprecated and will be "
> +                    "removed in the future.");
> +    }
> +
>      cpu_exec_realizefn(cs, &local_err);
>      if (local_err != NULL) {
>          error_propagate(errp, local_err);
> --
> 2.41.0
>
>