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 988CF2F5B for ; Wed, 30 Apr 2025 05:50:01 +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=1745992203; cv=none; b=ktF4Aj54M89CAzpmcDFl8r6nHnm+mqfiH1B0nkaolnazoF/E7LxOVA1D3VGB3EjFknr1ZLDg6QITE+esRtVs9fDgtuzWAhezJ96Kc7/uMJ+PQMekmRwYJ7wOhg52Py/Fuwhqhv3sJYCFbXRMvwrrTV1aAJp6dH0glIuPRcVt3I0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745992203; c=relaxed/simple; bh=tGpMwysnsq2TxilekSkNHmsw859wisrfWTcmDCeAUYs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BnK6OJgIcR7+ygz6tgporiLxzb7Bud4ydxv3et4orRDnB+JIMDlLhqj2C2iMahtLEbYtN/l9/KCrZDCa45X1K0C0QxvvuCLX7kxGnpoYSzYtQbNuPk7v5qwMRRrPu4+Iy/3TjIklQKnGnFK4TecWIvwjMaaKkNmsHYd1bXQUApw= 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 B3902106F; Tue, 29 Apr 2025 22:49:53 -0700 (PDT) Received: from [10.163.79.251] (unknown [10.163.79.251]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 327DD3F5A1; Tue, 29 Apr 2025 22:49:50 -0700 (PDT) Message-ID: <5eebef24-6c98-4407-a4f1-5a97f08b76a4@arm.com> Date: Wed, 30 Apr 2025 11:19:47 +0530 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 v2 4/7] arm64: Add batched version of ptep_modify_prot_start To: Anshuman Khandual , akpm@linux-foundation.org Cc: ryan.roberts@arm.com, david@redhat.com, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, peterx@redhat.com, joey.gouly@arm.com, ioworker0@gmail.com, baohua@kernel.org, kevin.brodsky@arm.com, quic_zhenhuah@quicinc.com, christophe.leroy@csgroup.eu, yangyicong@hisilicon.com, linux-arm-kernel@lists.infradead.org, namit@vmware.com, hughd@google.com, yang@os.amperecomputing.com, ziy@nvidia.com References: <20250429052336.18912-1-dev.jain@arm.com> <20250429052336.18912-5-dev.jain@arm.com> Content-Language: en-US From: Dev Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 30/04/25 11:13 am, Anshuman Khandual wrote: > On 4/29/25 10:53, Dev Jain wrote: >> Override the generic definition to use get_and_clear_full_ptes(), so that >> we do a TLBI possibly only on the "contpte-edges" of the large PTE block, >> instead of doing it for every contpte block, which happens for ptep_get_and_clear(). > > Could you please explain what does "contpte-edges" really signify in the > context of large PTE blocks ? Also how TLBI operation only on these edges > will never run into the risk of missing TLB invalidation of some other > mapped areas ? We are doing a TLBI over the whole range already, in the mprotect code: see tlb_flush_pte_range. What the arm64 internal API does, irrespective of the caller, is to do a TLBI for every contpte block in case of unfolding. We don't need that for the intermediate blocks because the caller does that. We do need a TLBI for the start and end contpte block, because in case the range we are invalidating partially covers them, then the caller will not do a TLBI for the non-overlapped PTEs of the block. I'll explain some more in the changelog next version. > >> >> Signed-off-by: Dev Jain >> --- >> arch/arm64/include/asm/pgtable.h | 5 +++++ >> arch/arm64/mm/mmu.c | 12 +++++++++--- >> include/linux/pgtable.h | 4 ++++ >> mm/pgtable-generic.c | 16 +++++++++++----- >> 4 files changed, 29 insertions(+), 8 deletions(-) >> >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >> index 2a77f11b78d5..8872ea5f0642 100644 >> --- a/arch/arm64/include/asm/pgtable.h >> +++ b/arch/arm64/include/asm/pgtable.h >> @@ -1553,6 +1553,11 @@ extern void ptep_modify_prot_commit(struct vm_area_struct *vma, >> unsigned long addr, pte_t *ptep, >> pte_t old_pte, pte_t new_pte); >> >> +#define modify_prot_start_ptes modify_prot_start_ptes >> +extern pte_t modify_prot_start_ptes(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep, >> + unsigned int nr); >> + >> #ifdef CONFIG_ARM64_CONTPTE >> >> /* >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index 8fcf59ba39db..fe60be8774f4 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -1523,7 +1523,8 @@ static int __init prevent_bootmem_remove_init(void) >> early_initcall(prevent_bootmem_remove_init); >> #endif >> >> -pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) >> +pte_t modify_prot_start_ptes(struct vm_area_struct *vma, unsigned long addr, >> + pte_t *ptep, unsigned int nr) >> { >> if (alternative_has_cap_unlikely(ARM64_WORKAROUND_2645198)) { >> /* >> @@ -1532,9 +1533,14 @@ pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte >> * in cases where cpu is affected with errata #2645198. >> */ >> if (pte_user_exec(ptep_get(ptep))) >> - return ptep_clear_flush(vma, addr, ptep); >> + return clear_flush_ptes(vma, addr, ptep, nr); >> } >> - return ptep_get_and_clear(vma->vm_mm, addr, ptep); >> + return get_and_clear_full_ptes(vma->vm_mm, addr, ptep, nr, 0); >> +} >> + >> +pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep) >> +{ >> + return modify_prot_start_ptes(vma, addr, ptep, 1); >> } >> >> void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep, >> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >> index ed287289335f..10cdb87ccecf 100644 >> --- a/include/linux/pgtable.h >> +++ b/include/linux/pgtable.h >> @@ -828,6 +828,10 @@ extern pte_t ptep_clear_flush(struct vm_area_struct *vma, >> pte_t *ptep); >> #endif >> >> +extern pte_t clear_flush_ptes(struct vm_area_struct *vma, >> + unsigned long address, >> + pte_t *ptep, unsigned int nr); >> + >> #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH >> extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, >> unsigned long address, >> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c >> index 5a882f2b10f9..e238f88c3cac 100644 >> --- a/mm/pgtable-generic.c >> +++ b/mm/pgtable-generic.c >> @@ -90,17 +90,23 @@ int ptep_clear_flush_young(struct vm_area_struct *vma, >> } >> #endif >> >> -#ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH >> -pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address, >> - pte_t *ptep) >> +pte_t clear_flush_ptes(struct vm_area_struct *vma, unsigned long address, >> + pte_t *ptep, unsigned int nr) >> { >> struct mm_struct *mm = (vma)->vm_mm; >> pte_t pte; >> - pte = ptep_get_and_clear(mm, address, ptep); >> + pte = get_and_clear_full_ptes(mm, address, ptep, nr, 0); >> if (pte_accessible(mm, pte)) >> - flush_tlb_page(vma, address); >> + flush_tlb_range(vma, address, address + nr * PAGE_SIZE); >> return pte; >> } >> + >> +#ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH >> +pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address, >> + pte_t *ptep) >> +{ >> + return clear_flush_ptes(vma, address, ptep, 1); >> +} >> #endif >> >> #ifdef CONFIG_TRANSPARENT_HUGEPAGE