Re: [PATCH 03/13] cpu/hotplug, x86/acpi: Disable CPU hotplug for ACPI MADT wakeup

[Huang, Kai]

>  /* Physical address of the Multiprocessor Wakeup Structure mailbox */
> @@ -74,6 +75,9 @@ int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
>  
>  	acpi_mp_wake_mailbox_paddr = mp_wake->base_address;
>  
> +	/* Disable CPU onlining/offlining */
> +	cpu_hotplug_not_supported();
> +

Both onlining/offlining are prevented, or just offlining?

The previous patch says:

	It does not prevent the initial bring up of the CPU, but it stops 
	subsequent offlining.

And ...

[...]


> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -1522,7 +1522,7 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
>  	 * If the platform does not support hotplug, report it explicitly to
>  	 * differentiate it from a transient offlining failure.
>  	 */
> -	if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED) || !cpu_hotplug_supported)
> +	if (!cpu_hotplug_supported)
>  		return -EOPNOTSUPP;
>  	if (cpu_hotplug_disabled)
>  		return -EBUSY;

... here cpu_down_maps_locked() only prevents offlining if I am reading
correctly.

Also, can we rename cpu_hotplug_supported to cpu_offline_supported to match the
behaviour better?

Anyway, isn't it a little bit odd to have:

	if (!cpu_hotplug_supported)
 		return -EOPNOTSUPP;
 	if (cpu_hotplug_disabled)
 		return -EBUSY;

?