Re: [PATCH 12/19] arm64: cpu_ops: Make 'cpu_operations' pointer global instead of per-cpu

[Jinjie Ruan <ruanjinjie@huawei.com>]

在 2026/9/8 0:40, Will Deacon 写道:
> 'cpu_ops' is an NR_CPUS-length array of 'cpu_operations' pointers, which
> theoretically allows for different CPUs to have different bringup and
> hotplug backends.
> 
> In reality, this complexity exists only to deal with the case where CPU0
> is not hotpluggable, so replace the array with a single, global pointer
> and record separately whether or not they apply to the boot CPU. Update
> the logic in init_cpu_ops() to enforce that only a single set of
> 'cpu_ops' is required.
> 
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/kernel/cpu_ops.c | 29 ++++++++++++++++++++---------
>  1 file changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
> index e133011f64b5..eacfb88a0c0c 100644
> --- a/arch/arm64/kernel/cpu_ops.c
> +++ b/arch/arm64/kernel/cpu_ops.c
> @@ -20,7 +20,8 @@ extern const struct cpu_operations acpi_parking_protocol_ops;
>  #endif
>  extern const struct cpu_operations cpu_psci_ops;
>  
> -static const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
> +static const struct cpu_operations *cpu_ops __ro_after_init;
> +static bool boot_cpu_has_enable_method __ro_after_init;
>  
>  static const struct cpu_operations *const dt_supported_cpu_ops[] __initconst = {
>  	&smp_spin_table_ops,
> @@ -40,6 +41,9 @@ static const struct cpu_operations * __init cpu_get_ops(const char *name)
>  {
>  	const struct cpu_operations *const *ops;
>  
> +	if (!name)
> +		return NULL;
> +
>  	ops = acpi_disabled ? dt_supported_cpu_ops : acpi_supported_cpu_ops;
>  
>  	while (*ops) {
> @@ -49,6 +53,7 @@ static const struct cpu_operations * __init cpu_get_ops(const char *name)
>  		ops++;
>  	}
>  
> +	pr_warn("Unsupported enable-method: %s\n", name);
>  	return NULL;
>  }
>  
> @@ -94,25 +99,31 @@ static const char *__init cpu_read_enable_method(int cpu)
>  	return enable_method;
>  }
>  /*
> - * Read a cpu's enable method and record it in cpu_ops.
> + * Read a cpu's enable method and update/check cpu_ops.
>   */
>  int __init init_cpu_ops(int cpu)
>  {
>  	const char *enable_method = cpu_read_enable_method(cpu);
> +	const struct cpu_operations *ops = cpu_get_ops(enable_method);
>  
> -	if (!enable_method)
> +	if (!ops)
>  		return -ENODEV;
>  
> -	cpu_ops[cpu] = cpu_get_ops(enable_method);
> -	if (!cpu_ops[cpu]) {
> -		pr_warn("Unsupported enable-method: %s\n", enable_method);
> -		return -EOPNOTSUPP;
> -	}
> +	if (!cpu_ops)
> +		cpu_ops = ops;
> +	else if (cpu_ops != ops)
> +		return -EBUSY;

Should we return the original error code of init_cpu_ops() in
smp_cpu_setup()?

 487 static int __init smp_cpu_setup(int cpu)
 488 {
 489 >-------const struct cpu_operations *ops;
 490
 491 >-------if (init_cpu_ops(cpu))
 492 >------->-------return -ENODEV;
 493
 494 >-------ops = get_cpu_ops(cpu);
 495 >-------if (ops->cpu_init(cpu))
 496 >------->-------return -ENODEV;


Otherwise LGTM
Reviewed-by: Jinjie Ruan <ruanjinjie@huawei.com>

> +
> +	if (cpu == 0)
> +		boot_cpu_has_enable_method = true;
>  
>  	return 0;
>  }
>  
>  const struct cpu_operations *get_cpu_ops(int cpu)
>  {
> -	return cpu_ops[cpu];
> +	if (cpu || boot_cpu_has_enable_method)
> +		return cpu_ops;
> +
> +	return NULL;

>  }