From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D5FCD253B58 for ; Wed, 24 Dec 2025 14:07:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766585272; cv=none; b=idfw3pvBG2pnml84whymiScD2ZuILKwPZyS6D6XzXwuSWXOUQsp8CfyMmU7HQKpI09/09P8hY2r2pPRyVX5Nowh1MGjo7BB/CDmTr1rupJvTab/6xe0Os6Cr/oTdU+n+nhpGPKtKJ0nOlH9MdqCMjHL7g01Ouos7YXPJnTvcavg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766585272; c=relaxed/simple; bh=z+1p7Sp0QKMY3e8dym6v6hDHZJuQmetIjpIk6/gayWQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=HLIIv7NoIvW3TM79n8/wKwKi2hrgJLh9pcee4LuTeAKcXCq8CAeg7F+LJqOo4v8nKO6ubyDRkkaesDHAMYuHMsNO+58gCsnLHqysi3P4KeBl0jN2eESX+mNyRQ5jTutLPky8C9hSS7/JaGiHhcI2WKzZD/3AyAe5fSi0dDcUy7I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0AA54339; Wed, 24 Dec 2025 06:07:32 -0800 (PST) Received: from [10.57.93.190] (unknown [10.57.93.190]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 290423F5A1; Wed, 24 Dec 2025 06:07:36 -0800 (PST) Message-ID: Date: Wed, 24 Dec 2025 14:07:34 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 3/5] arm64: mm: support batch clearing of the young flag for large folios Content-Language: en-GB To: Baolin Wang , akpm@linux-foundation.org, david@kernel.org, catalin.marinas@arm.com, will@kernel.org Cc: lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <3b427d9010a6d52f2b91342760f12be097d21cf6.1766455378.git.baolin.wang@linux.alibaba.com> From: Ryan Roberts In-Reply-To: <3b427d9010a6d52f2b91342760f12be097d21cf6.1766455378.git.baolin.wang@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 23/12/2025 05:48, Baolin Wang wrote: > Currently, contpte_ptep_test_and_clear_young() and contpte_ptep_clear_flush_young() > only clear the young flag and flush TLBs for PTEs within the contiguous range. > To support batch PTE operations for other sized large folios in the following > patches, adding a new parameter to specify the number of PTEs that map consecutive > pages of the same large folio in a single VMA and a single page table. > > While we are at it, rename the functions to maintain consistency with other > contpte_*() functions. > > Signed-off-by: Baolin Wang > --- > arch/arm64/include/asm/pgtable.h | 12 ++++++------ > arch/arm64/mm/contpte.c | 33 ++++++++++++++++++-------------- > 2 files changed, 25 insertions(+), 20 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 445e18e92221..d5fbe72e820a 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -1648,10 +1648,10 @@ extern void contpte_clear_full_ptes(struct mm_struct *mm, unsigned long addr, > extern pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, > unsigned long addr, pte_t *ptep, > unsigned int nr, int full); > -extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, > - unsigned long addr, pte_t *ptep); > -extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, > - unsigned long addr, pte_t *ptep); > +int contpte_test_and_clear_young_ptes(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep, unsigned int nr); > +int contpte_clear_flush_young_ptes(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep, unsigned int nr); > extern void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, unsigned int nr); > extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, > @@ -1823,7 +1823,7 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, > if (likely(!pte_valid_cont(orig_pte))) > return __ptep_test_and_clear_young(vma, addr, ptep); > > - return contpte_ptep_test_and_clear_young(vma, addr, ptep); > + return contpte_test_and_clear_young_ptes(vma, addr, ptep, CONT_PTES); As per your fixup patch, I agree that nr should be 1 here, not CONT_PTES. > } > > #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH > @@ -1835,7 +1835,7 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma, > if (likely(!pte_valid_cont(orig_pte))) > return __ptep_clear_flush_young(vma, addr, ptep); > > - return contpte_ptep_clear_flush_young(vma, addr, ptep); > + return contpte_clear_flush_young_ptes(vma, addr, ptep, CONT_PTES); And same here. > } > > #define wrprotect_ptes wrprotect_ptes > diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c > index e4ddeb46f25d..b929a455103f 100644 > --- a/arch/arm64/mm/contpte.c > +++ b/arch/arm64/mm/contpte.c > @@ -508,8 +508,9 @@ pte_t contpte_get_and_clear_full_ptes(struct mm_struct *mm, > } > EXPORT_SYMBOL_GPL(contpte_get_and_clear_full_ptes); > > -int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, > - unsigned long addr, pte_t *ptep) > +int contpte_test_and_clear_young_ptes(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep, > + unsigned int nr) > { > /* > * ptep_clear_flush_young() technically requires us to clear the access > @@ -518,41 +519,45 @@ int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, > * contig range when the range is covered by a single folio, we can get > * away with clearing young for the whole contig range here, so we avoid > * having to unfold. > + * > + * The 'nr' means consecutive (present) PTEs that map consecutive pages > + * of the same large folio in a single VMA and a single page table. > */ > > + unsigned long end = addr + nr * PAGE_SIZE; > int young = 0; > - int i; > > - ptep = contpte_align_down(ptep); > - addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); > - > - for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) > + ptep = contpte_align_addr_ptep(&addr, &end, ptep, nr); > + for (; addr != end; ptep++, addr += PAGE_SIZE) > young |= __ptep_test_and_clear_young(vma, addr, ptep); > > return young; > } > -EXPORT_SYMBOL_GPL(contpte_ptep_test_and_clear_young); > +EXPORT_SYMBOL_GPL(contpte_test_and_clear_young_ptes); > > -int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, > - unsigned long addr, pte_t *ptep) > +int contpte_clear_flush_young_ptes(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep, > + unsigned int nr) > { > int young; > > - young = contpte_ptep_test_and_clear_young(vma, addr, ptep); > + young = contpte_test_and_clear_young_ptes(vma, addr, ptep, nr); > > if (young) { > + unsigned long end = addr + nr * PAGE_SIZE; > + > + contpte_align_addr_ptep(&addr, &end, ptep, nr); > /* > * See comment in __ptep_clear_flush_young(); same rationale for > * eliding the trailing DSB applies here. > */ > - addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); > - __flush_tlb_range_nosync(vma->vm_mm, addr, addr + CONT_PTE_SIZE, > + __flush_tlb_range_nosync(vma->vm_mm, addr, end, > PAGE_SIZE, true, 3); Hmm... The requirement is that we must flush the _page_ if clearing access for a pte that does not have the contiguous bit set, or we must flush the _contpte block_ if clearing access for a pte that does have the contiguous bit set. With your changes, you may call for a large range that covers multiple contpte blocks but only has a single pte in a single contpte block for which the access bit was previously set. But that will cause flushing the TLB for the full range. Could this cause a performance issue? Yes, no, maybe... I think it's unlikely but I wouldn't rule it out in some edge case. I wonder if it's better to track the sub-ranges where access was cleared and only issue tlbi for those sub-ranges? Probably just keep it simple (the way you have done it) until/unless we see an actual problem? Thanks, Ryan > } > > return young; > } > -EXPORT_SYMBOL_GPL(contpte_ptep_clear_flush_young); > +EXPORT_SYMBOL_GPL(contpte_clear_flush_young_ptes); > > void contpte_wrprotect_ptes(struct mm_struct *mm, unsigned long addr, > pte_t *ptep, unsigned int nr)