linux-kernel - Re: [PATCH] powerpc/mm: Code cleanup for __hash_page

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Date: Tue, 27 Feb 2024 11:14:27 +0800
From: Kunwu Chan <chentao@...inos.cn>
To: Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com,
 christophe.leroy@...roup.eu, aneesh.kumar@...nel.org,
 naveen.n.rao@...ux.ibm.com
Cc: linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/mm: Code cleanup for __hash_page_thp

Thanks for the reply.

On 2024/2/26 18:49, Michael Ellerman wrote:
> Kunwu Chan <chentao@...inos.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
     */

> 
> cheers
> 
>> diff --git a/arch/powerpc/mm/book3s64/hash_hugepage.c b/arch/powerpc/mm/book3s64/hash_hugepage.c
>> index c0fabe6c5a12..127a3a2c174b 100644
>> --- a/arch/powerpc/mm/book3s64/hash_hugepage.c
>> +++ b/arch/powerpc/mm/book3s64/hash_hugepage.c
>> @@ -59,16 +59,6 @@ int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
>>   
>>   	rflags = htab_convert_pte_flags(new_pmd, flags);
>>   
>> -#if 0
>> -	if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) {
>> -
>> -		/*
>> -		 * No CPU has hugepages but lacks no execute, so we
>> -		 * don't need to worry about that case
>> -		 */
>> -		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
>> -	}
>> -#endif
>>   	/*
>>   	 * Find the slot index details for this ea, using base page size.
>>   	 */
>> -- 
>> 2.39.2
-- 
Thanks,
   Kunwu