Re: [PATCH] x86, smpboot: allow manual hotplug of CPUs

[Sasha Levin <sasha.levin@oracle.com>]

On 11/21/2012 02:24 PM, H. Peter Anvin wrote:
> On 11/21/2012 11:19 AM, Sasha Levin wrote:
>>>
>>> So, are there any mptables platforms which support hotplug?  If the
>>> answer is "KVM" then the answer is that KVM needs to move to ACPI to get
>>> the proper functionality; putting a hack in is really not okay.
>>
>> There are no platforms which support actual hotplug, but you can still set
>> existing processors as disabled in the table and without this patch there's
>> no way enable them.
>>
>> I'm not sure if it's a "hack" though - the presentation of hotpluggable cpus
>> is the almost the same between mptable and acpi, and acpi provides a way to
>> manually probe/release cpus as well. The only difference is that acpi also
>> provides notifications about such events.
>>
>> Actually, maybe acpi should start using probe/release as well... hmm...
>>
> 
> The bottom line is that I don't want the underlying implementation to
> end up with a user-visible difference... therein lies madness and lots
> of bugs.

Okay, so if in the case of ACPI, 'probe' will call acpi_processor_add()
and 'release' would call acpi_processor_remove() so the behaviour
would be the same for both ACPI and mptables. Is this okay?


Thanks,
Sasha