Re: [PATCH 0/8] implement "memmap on memory" feature on s390

David Hildenbrand
2023-11-17T15:38:02Z

On 17.11.23 14:56, Sumanth Korikkar wrote:
> On Fri, Nov 17, 2023 at 12:08:31AM +0100, David Hildenbrand wrote:
>> On 14.11.23 19:02, Sumanth Korikkar wrote:
>>> Hi All,
>>>
>>> The patch series implements "memmap on memory" feature on s390 and
>>> provides the necessary fixes for it.
>>
>> Thinking about this, one thing that makes s390x different from all the other
>> architectures in this series is the altmap handling.
>>
>> I'm curious, why is that even required?
>>
>> A memmep that is not marked as online in the section should not be touched
>> by anybody (except memory onlining code :) ). And if we do, it's usually a
>> BUG because that memmap might contain garbage/be poisoned or completely
>> stale, so we might want to track that down and fix it in any case.
>>
>> So what speaks against just leaving add_memory() populate the memmap from
>> the altmap? Then, also the page tables for the memmap are already in place
>> when onlining memory.
>>
>
> we do have page_init_poison() in sparse_add_section() which should be
> handled later then. not in add_pages()

Was that all, or did you stumble over other things?

--
Cheers,

David / dhildenb