linux-kernel - Re: [PATCH v5 7/7] arm64: Add batched versions of ptep_modify_prot

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Message-ID: <aH5jbAYKoACvspj4@arm.com>
Date: Mon, 21 Jul 2025 16:57:32 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Dev Jain <dev.jain@....com>
Cc: akpm@...ux-foundation.org, ryan.roberts@....com, david@...hat.com,
	willy@...radead.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, will@...nel.org,
	Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, vbabka@...e.cz,
	jannh@...gle.com, anshuman.khandual@....com, peterx@...hat.com,
	joey.gouly@....com, ioworker0@...il.com, baohua@...nel.org,
	kevin.brodsky@....com, quic_zhenhuah@...cinc.com,
	christophe.leroy@...roup.eu, yangyicong@...ilicon.com,
	linux-arm-kernel@...ts.infradead.org, hughd@...gle.com,
	yang@...amperecomputing.com, ziy@...dia.com
Subject: Re: [PATCH v5 7/7] arm64: Add batched versions of
 ptep_modify_prot_start/commit

On Fri, Jul 18, 2025 at 02:32:44PM +0530, Dev Jain wrote:
> Override the generic definition of modify_prot_start_ptes() to use
> get_and_clear_full_ptes(). This helper does a TLBI only for the starting
> and ending contpte block of the range, whereas the current implementation
> will call ptep_get_and_clear() for every contpte block, thus doing a
> TLBI on every contpte block. Therefore, we have a performance win.
> 
> The arm64 definition of pte_accessible() allows us to batch in the
> errata specific case:
> 
> #define pte_accessible(mm, pte)	\
> 	(mm_tlb_flush_pending(mm) ? pte_present(pte) : pte_valid(pte))
> 
> All ptes are obviously present in the folio batch, and they are also valid.
> 
> Override the generic definition of modify_prot_commit_ptes() to simply
> use set_ptes() to map the new ptes into the pagetable.
> 
> Reviewed-by: Ryan Roberts <ryan.roberts@....com>
> Signed-off-by: Dev Jain <dev.jain@....com>

The arm64 changes look fine to me:

Reviewed-by: Catalin Marinas <catalin.marinas@....com>