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Re: [RFC PATCH] target/arm/arm-powerctl: Restrict to ARM cores


From: Peter Maydell
Subject: Re: [RFC PATCH] target/arm/arm-powerctl: Restrict to ARM cores
Date: Mon, 6 Jan 2025 21:45:01 +0000

On Mon, 6 Jan 2025 at 18:23, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
>
> When running on a heterogeneous setup, the CPU_FOREACH()
> macro in arm_get_cpu_by_id() iterates on all vCPUs,
> regardless they are ARM or not. Check the CPU class type
> and skip the non-ARM instances.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  target/arm/arm-powerctl.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/target/arm/arm-powerctl.c b/target/arm/arm-powerctl.c
> index 20c70c7d6bb..a080a6ab79f 100644
> --- a/target/arm/arm-powerctl.c
> +++ b/target/arm/arm-powerctl.c
> @@ -36,9 +36,11 @@ CPUState *arm_get_cpu_by_id(uint64_t id)
>      DPRINTF("cpu %" PRId64 "\n", id);
>
>      CPU_FOREACH(cpu) {
> -        ARMCPU *armcpu = ARM_CPU(cpu);
> +        if (!object_class_dynamic_cast((ObjectClass *)cpu->cc, 
> TYPE_ARM_CPU)) {
> +            continue;
> +        }
>
> -        if (arm_cpu_mp_affinity(armcpu) == id) {
> +        if (arm_cpu_mp_affinity((ARMCPU *)cpu) == id) {
>              return cpu;
>          }
>      }
> --

Makes sense -- the function is "get me a CPU with this MPIDR",
so in a heterogenous system we can happily scan all the Arm CPUs
(even if they're in some other SoC) and trust that the caller
passed us a MPIDR that makes sense. (The callsites might need
some work if we wanted to use those SoC models in a heterogenous
setup where they're not the only SoC -- eg the imx6_src devices
assume the CPUs in the SoC are numbered 0,1,2,3 -- but we don't
need to do that now.)

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM



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