linux-kernel - Re: [PATCH v4 10/15] riscv: pgtable: move pagetable_dtor() to __tlb_remove

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Message-ID: <fca0d7de-b563-4d11-9ed8-c6b8290c4cf9@bytedance.com>
Date: Tue, 7 Jan 2025 20:31:10 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: Kevin Brodsky <kevin.brodsky@....com>
Cc: agordeev@...ux.ibm.com, palmer@...belt.com, tglx@...utronix.de,
 david@...hat.com, jannh@...gle.com, hughd@...gle.com, yuzhao@...gle.com,
 willy@...radead.org, muchun.song@...ux.dev, vbabka@...nel.org,
 lorenzo.stoakes@...cle.com, rientjes@...gle.com, vishal.moola@...il.com,
 arnd@...db.de, will@...nel.org, aneesh.kumar@...nel.org, npiggin@...il.com,
 dave.hansen@...ux.intel.com, rppt@...nel.org, ryan.roberts@....com,
 linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
 linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
 linux-s390@...r.kernel.org, sparclinux@...r.kernel.org,
 linux-kernel@...r.kernel.org, x86@...nel.org, linux-arch@...r.kernel.org,
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 linux-sh@...r.kernel.org, linux-um@...ts.infradead.org,
 peterz@...radead.org, akpm@...ux-foundation.org
Subject: Re: [PATCH v4 10/15] riscv: pgtable: move pagetable_dtor() to
 __tlb_remove_table()



On 2025/1/7 19:58, Kevin Brodsky wrote:
> On 07/01/2025 11:51, Qi Zheng wrote:
>> [...]
>>
>> Author: Qi Zheng <zhengqi.arch@...edance.com>
>> Date:   Fri Dec 13 17:13:48 2024 +0800
>>
>>      mm: pgtable: completely move pagetable_dtor() to generic
>> tlb_remove_table()
>>
>>      For the generic tlb_remove_table(), it is implemented in the
>> following two
>>      forms:
>>
>>      1) CONFIG_MMU_GATHER_TABLE_FREE is enabled
>>
>>      tlb_remove_table
>>      --> generic __tlb_remove_table()
>>
>>      2) CONFIG_MMU_GATHER_TABLE_FREE is disabled
>>
>>      tlb_remove_table
>>      --> tlb_remove_page
>>
>>      For case 1), the pagetable_dtor() has already been moved to generic
>>      __tlb_remove_table().
>>
>>      For case 2), now only arm will call
>> tlb_remove_table()/tlb_remove_ptdesc()
>>      when CONFIG_MMU_GATHER_TABLE_FREE is disabled. Let's move
>> pagetable_dtor()
>>      completely to generic tlb_remove_table(), so that the
>> architectures can
>>      follow more easily.
>>
>>      Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>

I missed your Suggested-by, will add it in v5.

>>
>> diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
>> index b8eebdb598631..ea4fbe7b17f6f 100644
>> --- a/arch/arm/include/asm/tlb.h
>> +++ b/arch/arm/include/asm/tlb.h
>> @@ -34,10 +34,6 @@ __pte_free_tlb(struct mmu_gather *tlb, pgtable_t
>> pte, unsigned long addr)
>>   {
>>          struct ptdesc *ptdesc = page_ptdesc(pte);
>>
>> -#ifndef CONFIG_MMU_GATHER_TABLE_FREE
>> -       pagetable_dtor(ptdesc);
>> -#endif
> 
> I guess this hunk will disappear since this call isn't present to start
> with.

Yes, I plan to add this in the patch #8, and remove it in this patch.

> 
>> -
>>   #ifndef CONFIG_ARM_LPAE
>>          /*
>>           * With the classic ARM MMU, a pte page has two corresponding pmd
>> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
>> index 69de47c7ef3c5..53ae7748f555b 100644
>> --- a/include/asm-generic/tlb.h
>> +++ b/include/asm-generic/tlb.h
>> @@ -220,14 +220,20 @@ static inline void __tlb_remove_table(void *table)
>>
>>   extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
>>
>> -#else /* !CONFIG_MMU_GATHER_HAVE_TABLE_FREE */
>> +#else /* !CONFIG_MMU_GATHER_TABLE_FREE */
> 
> Good catch!
> 
>>
>> +static inline void tlb_remove_page(struct mmu_gather *tlb, struct
>> page *page);
> 
> Nit: might be better to move the declaration up, e.g. above #ifdef
> CONFIG_MMU_GATHER_TABLE_FREE.

Now only the tlb_remove_table() below calls it, maybe it's better to
keep the impact to minimum?

> 
>>   /*
>>    * Without MMU_GATHER_TABLE_FREE the architecture is assumed to have
>> page based
>>    * page directories and we can use the normal page batching to free
>> them.
>>    */
>> -#define tlb_remove_table(tlb, page) tlb_remove_page((tlb), (page))
>> +static inline void tlb_remove_table(struct mmu_gather *tlb, void *table)
>> +{
>> +       struct page *page = (struct page *)table;
>>
>> +       pagetable_dtor(page_ptdesc(page));
>> +       tlb_remove_page(tlb, page);
>> +}
>>   #endif /* CONFIG_MMU_GATHER_TABLE_FREE */
>>
>>   #ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
> 
> Looks good to me otherwise.

I will add your Reviewed-by to all patches (except yours) in v5, can
I also add it to this new added patch? (if we agree with the discussion
above) ;)

Thanks!

> 
> - Kevin