From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C007D3D8123 for ; Thu, 16 Jul 2026 09:41:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784194909; cv=none; b=b4/eQpZibUKPGsHwtFYKHIxVamuPJBHV5nkaU45zMjQ+GFLzVqJkQk2EUPYhAedQSkTwE2iVgANhNPy4loJwy9Ur8aMqDxgI6tEFTR3gXPp7Gs2JhztDIj/bAt5mAGm09itBcjLWyuoEgZ5ukSMRajjmZOoO9lats+Pa9QM2rbI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784194909; c=relaxed/simple; bh=T5dWz7yCGmXseZatuYNS1jb8YcMJojFo3UnBsIeRqf4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fPWPZjuJu0tqXvNhLjbZDDaNdCkwTsuMUw9RKc1Xrsfj5yz1XKzuIhTC0tegG2VfBOyfvS7kXe1J0rmVlCN2HTXAXOUHMV2+AEfvVaiKRr1t6nO76AZd+vBqEAmVe4ZfLSCDcLr0BHHwQI0IRkwGykXL2oBH6zkc4Y+/syiaSsg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P/ugcmEq; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="P/ugcmEq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5AD01F000E9; Thu, 16 Jul 2026 09:41:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784194905; bh=ux8ETJECpvvPUV8iT6ysQIof/guD9S9sQn0Lz1zlg+Q=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=P/ugcmEqIuhtqa7Cq6GkVlW+vWSfXi/dB7/1JYp0Orl2VyGxDmNe+pylJGYVE6a1l RuSe5r9MoP+Yu9YJT8km1sfE9AcnCHSRY2SHRVnmnki+EzselqOcW11wa5VusoMiRq o9LHDYwBO+WrlE/Ry3tdSQQxqw0A6gJ+rS+TQ/zyYNbi7dbZmPiL5W4Ol4QJzdXXO9 75Hkp2QvLkiY2wLKDAYa/N2G/ZLgNVz3D0uBGKuYTxOApsRnxpRodKiZkGAyC6EUax muofYK4wAS0WkaVfPorsOWc2lvKZzUO+wDuTGq9bu/VE5GFRCe8iUUXzHvmD61KM7+ Ee/e07RodctCg== Message-ID: <7e44ac28-2624-4440-ae77-059eff00c202@kernel.org> Date: Thu, 16 Jul 2026 11:41:40 +0200 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 2/3] mm/memory: batch set uffd-wp markers during zapping To: Dev Jain , akpm@linux-foundation.org, ljs@kernel.org Cc: liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, riel@surriel.com, harry@kernel.org, jannh@google.com, lance.yang@linux.dev, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20260715111839.1667914-1-dev.jain@arm.com> <20260715111839.1667914-3-dev.jain@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/15/26 13:18, Dev Jain wrote: > Enable batch setting of uffd-wp ptes. > > The code paths passing nr > 1 to zap_install_uffd_wp_if_needed() produce > that nr through either folio_pte_batch or swap_pte_batch, therefore > batching is correct: > > 1) all ptes belong to the same type of VMA (anonymous or non-anonymous, > wp-armed or non-wp-armed) > > 2) all ptes being marked with uffd-wp or all being not marked (same is the > case with the pte_swp_uffd_wp_any check) > > 3) uffd_supports_wp_marker() is independent of the function parameters > > Note that we will have to use set_pte_at() in a loop instead of set_ptes() > since the latter cannot handle present->non-present conversion for > nr_pages > 1. > > Rename the function to cond_install_uffd_wp_ptes. > > Signed-off-by: Dev Jain > --- > To handle nonpresent->nonpresent transition in the ptes, we can have a > set_nonpresent_ptes() (in my unmap series) : if !softleaf_has_pfn(), use > set the same pte value to all ptep's in the patch. if softleaf_has_pfn(), > then add a softleaf_next_pfn() to construct the next softleaf, and > pte_next_softleaf() to call softleaf_next_pfn() and preserve the > wp bit, s-d bit, etc from the previous pte. > > include/linux/mm.h | 6 +++-- > mm/memory.c | 64 +++++++++++++++++----------------------------- > mm/rmap.c | 2 +- > 3 files changed, 29 insertions(+), 43 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index a71341c44655e..94e0a92bc70b1 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -5406,6 +5406,8 @@ void map_anon_folio_pte_nopf(struct folio *folio, pte_t *pte, > struct vm_area_struct *vma, unsigned long addr, > bool uffd_wp); > > -bool pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, > - unsigned long addr, pte_t *ptep, pte_t pte); > +bool cond_install_uffd_wp_ptes(struct vm_area_struct *vma, unsigned long addr, > + pte_t *ptep, pte_t pte, > + unsigned long nr_ptes); Two tab ... > + > #endif /* _LINUX_MM_H */ > diff --git a/mm/memory.c b/mm/memory.c > index 98b3ace15cef2..5d2b567b383d4 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1676,27 +1676,29 @@ static inline bool zap_drop_markers(struct zap_details *details) > } > > /** > - * pte_install_uffd_wp_if_needed - install uffd-wp marker after clearing a PTE > - * @vma: The VMA the page is mapped into. > - * @addr: Address the page is mapped at. > - * @ptep: Page table pointer for this entry. > + * cond_install_uffd_wp_ptes - install uffd-wp markers after clearing PTEs > + * @vma: The VMA the pages are mapped into. > + * @addr: Address the first page of this batch is mapped at. > + * @ptep: Page table pointer for the first entry of this batch. > * @pte: Old value of the entry pointed to by @ptep. > + * @nr_ptes: Number of entries to install. > * > - * If the PTE was write-protected by uffd-wp in any form, arm a special PTE > - * to replace a none PTE. NOTE! This should only be called when the PTE is > - * already cleared so we will never accidentally replace something valuable. > - * Meanwhile none PTEs also mean we are not demoting the PTE so a TLB flush is > - * not needed. E.g., when the PTE was cleared, the caller should have taken care > - * of the TLB flush. > + * If the PTEs were write-protected by uffd-wp in any form, arm special > + * PTEs to replace none PTEs. NOTE! This should only be called when the PTEs > + * are already cleared so we will never accidentally replace something > + * valuable. Meanwhile none PTEs also mean we are not demoting the PTEs so a > + * TLB flush is not needed. E.g., when PTEs were cleared, the caller should > + * have taken care of the TLB flush. > * > - * Must be called with the page table lock held so that no thread will see the > - * none PTE, and if they see it, they'll fault and serialize at the page table > - * lock. > + * Must be called with the page table lock held so that no thread will see > + * the none PTEs, and if they see them, they'll fault and serialize at the > + * page table lock. > * > - * Returns true if an uffd-wp PTE was installed, false otherwise. > + * Returns true if uffd-wp PTEs were installed, false otherwise. > */ > -bool pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, > - unsigned long addr, pte_t *ptep, pte_t pte) > +bool cond_install_uffd_wp_ptes(struct vm_area_struct *vma, > + unsigned long addr, pte_t *ptep, pte_t pte, > + unsigned long nr_ptes) > { > bool arm_uffd_pte = false; > > @@ -1726,13 +1728,14 @@ bool pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, > if (unlikely(pte_swp_uffd_any(pte))) > arm_uffd_pte = true; > > - if (unlikely(arm_uffd_pte)) { > + if (likely(!arm_uffd_pte)) > + return false; > + > + for (unsigned long i = 0; i < nr_ptes; ++i, ++ptep, addr += PAGE_SIZE) > set_pte_at(vma->vm_mm, addr, ptep, > make_pte_marker(PTE_MARKER_UFFD_WP)); > - return true; > - } Can we keep the "for (;;)" style of iterating PTEs that we use elsewhere? > > - return false; > + return true; > } > > /* > @@ -1746,29 +1749,10 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma, > unsigned long addr, pte_t *pte, int nr, > struct zap_details *details, pte_t pteval) > { > - bool was_installed = false; > - > - if (!uffd_supports_wp_marker()) > - return false; > - > - /* Zap on anonymous always means dropping everything */ > - if (vma_is_anonymous(vma)) > - return false; > - > if (zap_drop_markers(details)) > return false; > > - for (;;) { > - /* the PFN in the PTE is irrelevant. */ > - if (pte_install_uffd_wp_if_needed(vma, addr, pte, pteval)) > - was_installed = true; > - if (--nr == 0) > - break; > - pte++; > - addr += PAGE_SIZE; > - } > - > - return was_installed; > + return cond_install_uffd_wp_ptes(vma, addr, pte, pteval, nr); > } > > static __always_inline void zap_present_folio_ptes(struct mmu_gather *tlb, > diff --git a/mm/rmap.c b/mm/rmap.c > index ad820fe86f7d8..2f938d0ac6953 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -2345,7 +2345,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, > * we may want to replace a none pte with a marker pte if > * it's file-backed, so we don't lose the tracking info. > */ > - pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval); > + cond_install_uffd_wp_ptes(vma, address, pvmw.pte, pteval, 1); Was about to ask whether we should provide a wrapper, but the next patch converts this case. -- Cheers, David