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 CBE77343D80 for ; Thu, 16 Jul 2026 10:08:34 +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=1784196516; cv=none; b=EBg/22uEmi5VEwgHAEbgLyzweTIlRol1iSu+EWHbn0dyMYSYErpY2d2BbUgBwsFbibD36CzgiJ/HAKWCq6dev1I3pX0ibNRQ8ug71MBPEoQZv3yviaaHPoX2GIy7ssGXHZdno3k09aRSFFBtXqky00AvB8MXFdV7j0e4z1v6zjA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784196516; c=relaxed/simple; bh=NKlvIcjZUOffFTl9XBKSOaCSSdkSjxoXIP0NhQe8Pws=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=f8IAB37878ZCI3Ga8CxbDNOEmvqZzYuLiYkO6NNJ6IpezZ94VO553Zxk/Q7jMT7Orw4X7GxYu+zmLm+uUnygBiq1Gf3N8KKMet7MN+5TINX6QPt5mMIb/03MdiJmerqTWlasQc7ByE0vdSfZSK5NIjc95ThuqJWGENd7gIEKlj8= 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; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=HJT3om/R; 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="HJT3om/R" 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 BEF142F; Thu, 16 Jul 2026 03:08:29 -0700 (PDT) Received: from [10.164.19.52] (unknown [10.164.19.52]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 325C23F7B4; Thu, 16 Jul 2026 03:08:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784196514; bh=NKlvIcjZUOffFTl9XBKSOaCSSdkSjxoXIP0NhQe8Pws=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=HJT3om/RpvEtpRNp34ArkVaMtuDbr8K9CwCDhF5Lj6kgKkJ8e87nWt06DVuM9+koE iE2176tgLOFT2m4CC+sQq9fqmBfRZjl3CqQgQiQ1khxnksMXKu3XsLQd/EubHS/llO w9Lac16QFYyfvB+C5MfzNEWfWZ7RIXsNQKzksjnY= Message-ID: <01ef03b0-0b41-4c06-9c5d-d1bc118a6922@arm.com> Date: Thu, 16 Jul 2026 15:38:25 +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 2/3] mm/memory: batch set uffd-wp markers during zapping To: "David Hildenbrand (Arm)" , 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> <7e44ac28-2624-4440-ae77-059eff00c202@kernel.org> Content-Language: en-US From: Dev Jain In-Reply-To: <7e44ac28-2624-4440-ae77-059eff00c202@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/07/26 3:11 pm, David Hildenbrand (Arm) wrote: > 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 ... Ok. > >> + >> #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? Ok. > >> >> - 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. >