Re: [PATCH v1 3/4] arm/sysctl: Implement cpu hotplug ops

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.09.2025 15:35, Julien Grall wrote:
> On 18/09/2025 13:16, Mykyta Poturai wrote:
>> +static long cpu_hotplug_sysctl(struct xen_sysctl_cpu_hotplug *hotplug)
>> +{
>> +    bool up;
>> +
>> +    switch (hotplug->op) {
>> +        case XEN_SYSCTL_CPU_HOTPLUG_ONLINE:
>> +            if ( hotplug->cpu == 0 )
> 
> I can't find a similar check on x86. Do you have any pointer?

When CPU 0 cannot be brought down (see cpu_down()), tryin to bring it up
is kind of pointless, and hence can perhaps be short circuited like this?

Jan