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Subject: Re: [PATCH v3 02/11] s390x/mm: Fail when an altmap is used for
 arch_add_memory()
To: Michal Hocko <mhocko@kernel.org>
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Cc: Oscar Salvador <osalvador@suse.com>, linux-s390@vger.kernel.org,
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On 01.07.19 14:46, Michal Hocko wrote:
> On Mon 01-07-19 09:43:06, Michal Hocko wrote:
>> On Mon 27-05-19 13:11:43, David Hildenbrand wrote:
>>> ZONE_DEVICE is not yet supported, fail if an altmap is passed, so we
>>> don't forget arch_add_memory()/arch_remove_memory() when unlocking
>>> support.
>>
>> Why do we need this? Sure ZONE_DEVICE is not supported for s390 and so
>> might be the case for other arches which support hotplug. I do not see
>> much point in adding warning to each of them.
> 
> I would drop this one. If there is a strong reason to have something
> like that it should come with a better explanation and it can be done on
> top.
> 

This was requested by Dan and I agree it is the right thing to do. In
the context of paravirtualized devices (e.g., virtio-pmem), it makes
sense to block functionality an arch does not support.

I'll leave the decision to Andrew.

-- 

Thanks,

David / dhildenb