Re: [PATCH v2 2/2] arm64: mmu: avoid allocating pages while installing ng-mapping for KPTI

David Hildenbrand (Red Hat)
2025-12-18T08:46:17Z

On 12/18/25 09:37, Yeoreum Yun wrote:
> [...]
>>> I think it would be better to use only __GFP_HIGH in here since
>>> when kpti_install_ng_mappings() is called, "kswpd" doesn't created yet.
>>> and to allocate page with assurance, It would be good to use
>>> min_reserved to.
>>>
>>> Am I missing something?
>>
>> Personally I think we should just use "GFP_KERNEL | __GFP_ZERO". Anything else
>> would make this allocation look special, which it is not. If we fail to allocate
>> at this point in boot, we have bigger problems.
>
> But I'm not sure *HOW effective* to use GFP_KERNEL in here.
> Since it's before the any filesystem inited.
> IOW, in this context, almost there would be no *page cache*
> and I think it seems meaningless to use "GFP_KERNEL" and "direct
> reclaim"
>
> So to get success for allocation, __GFP_HIGH | _GFP_ZERO seems much
> better.

Unless there is a real reason to confuse readers why this is very
special, just go with "GFP_KERNEL | __GFP_ZERO", really.

In particular if it doesn't matter in practice? Or does it and we are
not getting your point?

--
Cheers

David