linux-kernel - Re: [PATCH 0/5] remove tlb_remove_page

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Message-ID: <65710478-4ee0-499e-9f66-dff81e226042@bytedance.com>
Date: Fri, 24 Jan 2025 21:04:02 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: kevin.brodsky@....com, riel@...riel.com, vishal.moola@...il.com,
 david@...hat.com, jannh@...gle.com, hughd@...gle.com, willy@...radead.org,
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 linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
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 linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 0/5] remove tlb_remove_page_ptdesc()



On 2025/1/24 19:47, Peter Zijlstra wrote:
> On Thu, Jan 23, 2025 at 09:26:13PM +0800, Qi Zheng wrote:
>> Hi all,
>>
>> As suggested by Peter Zijlstra below [1], this series aims to remove
>> tlb_remove_page_ptdesc().
>>
>> : Fundamentally tlb_remove_page() is about removing *pages* as from a PTE,
>> : there should not be a page-table anywhere near here *ever*.
>> :
>> : Yes, some architectures use tlb_remove_page() for page-tables too, but
>> : that is more or less an implementation detail that can be fixed.
>>
>> After this series, all architectures use tlb_remove_table() or tlb_remove_ptdesc()
>> to remove the page table pages. In the future, once all architectures using
>> tlb_remove_table() have also converted to using struct ptdesc (eg. powerpc), it
>> may be possible to use only tlb_remove_ptdesc().
> 
> Right, so I don't think Sparc and Power care to use ptdesc, they're
> using non page page-tables.
> 
> At the very least we should do something like this, the only point of
> having tlb_remove_ptdesc() is type safety, there really is no benefit
> from it in any other way.
> 
> ---
> diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
> index dec030cb1210..a6731328db6f 100644
> --- a/include/asm-generic/tlb.h
> +++ b/include/asm-generic/tlb.h
> @@ -504,7 +504,7 @@ static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
>   	return tlb_remove_page_size(tlb, page, PAGE_SIZE);
>   }
>   
> -static inline void tlb_remove_ptdesc(struct mmu_gather *tlb, void *pt)
> +static inline void tlb_remove_ptdesc(struct mmu_gather *tlb, struct ptdesc *pt)
>   {
>   	tlb_remove_table(tlb, pt);
>   }

Ah, make sense. I think this can be added to the patch #1.

Thanks!