Re: [PATCH v1 2/8] powerpc: hugetlb: Convert set_huge_pte_at() to take vma

Christophe Leroy
2023-09-22T09:14:46Z

Le 22/09/2023 à 10:41, Ryan Roberts a écrit :
> On 22/09/2023 09:10, Christophe Leroy wrote:
>>
>>
>>> I'm happy to take your proposed approach if that's your preference. Another
>>> option is to use a dummy VMA, as I have done in the core code, for the one call
>>> site that calls set_huge_pte_at() with init_mm:
>>>
>>> struct vm_area_struct vma = TLB_FLUSH_VMA(&init_mm, 0);
>>>
>>> This is an existing macro that creates a dummy vma with vma->vm_mm filled in.
>>> Then I pass &vma to the function.
>>
>> I don't like that, I prefer the solution I proposed. We already have a
>> couple places where powerpc do things based on whether vma is NULL or not.
>>
>>>
>>> Or yet another option would be to keep the mm param as is in set_huge_pte_at(),
>>> and add a size param to the function. But then all call sites have the burden of
>>> figuring out the size of the huge pte (although I think most know already).
>>
>> Indeed.
>>
>> arch_make_huge_pte() used to take a vma until commit 79c1c594f49a
>> ("mm/hugetlb: change parameters of arch_make_huge_pte()").
>>
>> Should we try and have the same approach ? Or is it irrelevant ?
>
> See [1]; I'm going to rework to pass mm + size parameter since the current
> approach will break riscv.

Can you pass a shift parameter instead of a size, like
arch_make_huge_pte() ? As far as I remember it is easier to handle a
shift than a size.

Christophe