Re: [PATCH] powerpc/mm: Code cleanup for __hash_page_thp

Kunwu Chan
2024-02-29T09:29:47Z

Thanks all for the reply.
On 2024/2/29 14:18, Michael Ellerman wrote:
> Aneesh Kumar K.V <aneesh.kumar@kernel.org> writes:
>> Michael Ellerman <mpe@ellerman.id.au> writes:
>>> Kunwu Chan <chentao@kylinos.cn> writes:
>>>> On 2024/2/26 18:49, Michael Ellerman wrote:
>>>>> Kunwu Chan <chentao@kylinos.cn> writes:
>>>>>> This part was commented from commit 6d492ecc6489
>>>>>> ("powerpc/THP: Add code to handle HPTE faults for hugepages")
>>>>>> in about 11 years before.
>>>>>>
>>>>>> If there are no plans to enable this part code in the future,
>>>>>> we can remove this dead code.
>>>>>
>>>>> I agree the code can go. But I'd like it to be replaced with a comment
>>>>> explaining what the dead code was trying to say.
>>>
>>>> Thanks, i'll update a new patch with the following comment:
>>>> /*
>>>> * No CPU has hugepages but lacks no execute, so we
>>>> * don't need to worry about cpu no CPU_FTR_COHERENT_ICACHE feature case
>>>> */
>>>
>>> Maybe wait until we can get some input from Aneesh. I'm not sure the
>>> code/comment are really up to date.
>>
>> How about?
>>
>> modified arch/powerpc/mm/book3s64/hash_hugepage.c
>> @@ -58,17 +58,13 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
>> return 0;
>>
>> rflags = htab_convert_pte_flags(new_pmd, flags);
>> + /*
>> + * THPs are only supported on platforms that can do mixed page size
>> + * segments (MPSS) and all such platforms have coherent icache. Hence we
>> + * don't need to do lazy icache flush (hash_page_do_lazy_icache()) on
>> + * noexecute fault.
>> + */
>
I'll use this comment in v2 patch.
And add two Suggested-by: label for you.

> Yeah thanks that looks good.
>
> It could say "see eg. __hash_page_4K()", but that's probably unnecessary
> as it mentions hash_page_do_lazy_icache(), and anyone interested is just
> going to grep for that anyway.
>
> cheers
--
Thanks,
Kunwu