Re: [PATCH RFCv2 3/4] mm/memory_hotplug: Introduce and use more memory types

David Hildenbrand
2018-12-04T09:47:33Z

On 04.12.18 10:44, Michal Suchánek wrote:
> On Fri, 30 Nov 2018 18:59:21 +0100
> David Hildenbrand <david@redhat.com> wrote:
>
>> Let's introduce new types for different kinds of memory blocks and use
>> them in existing code. As I don't see an easy way to split this up,
>> do it in one hunk for now.
>>
>> acpi:
>> Use DIMM or DIMM_UNREMOVABLE depending on hotremove support in the kernel.
>> Properly change the type when trying to add memory that was already
>> detected and used during boot (so this memory will correctly end up as
>> "acpi" in user space).
>>
>> pseries:
>> Use DIMM or DIMM_UNREMOVABLE depending on hotremove support in the kernel.
>> As far as I see, handling like in the acpi case for existing blocks is
>> not required.
>>
>> probed memory from user space:
>> Use DIMM_UNREMOVABLE as there is no interface to get rid of this code
>> again.
>>
>> hv_balloon,xen/balloon:
>> Use BALLOON. As simple as that :)
>>
>> s390x/sclp:
>> Use a dedicated type S390X_STANDBY as this type of memory and it's
>> semantics are very s390x specific.
>>
>> powernv/memtrace:
>> Only allow to use BOOT memory for memtrace. I consider this code in
>> general dangerous, but we have to keep it working ... most probably just
>> a debug feature.
>
> I don't think it should be arbitrarily restricted like that.
>

Well code that "randomly" offlines/onlines/removes/adds memory blocks
that it does not own (hint: nobody else in the kernel does that), should
be restricted to types we can guarantee to work.

> Thanks
>
> Michal
>

--

Thanks,

David / dhildenb