Subject: ARM64: CPU Hotplug: can't enable more cpus than maxcpus value (kernel 4.5)

From: [email-masked] (Suzuki K. Poulose)
Date: Thu, 3 Mar 2016 15:01:00 +0000

On 03/03/16 14:59, Suzuki K. Poulose wrote:
> On 03/03/16 14:42, Mark Rutland wrote:
>
>>> However for arm64 it is implemented that cpu_present_mask is
>>> explicetely set accordingly to 'maxcpus' value. Is it design intent ?
>>
>> To some extent, yes.
>>
>> Due to the possibility of a heterogeneous system, we must bring all CPUs
>> online at boot time, and cannot defer this.
>>
>> This is necessary to detect the common subset of supported features, and
>> also to detect the full set of CPUs in the system to correctly apply
>> errata workarounds which require kernel text patching.
>
> We don't have this limitation anymore, as we can check if the booting CPU

s/we can/we do/

for the hotplugged CPUs.

Cheers
Suzuki