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 6F96548C3FF; Wed, 2 Sep 2026 11:57:30 +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=1788350261; cv=none; b=tgIl5OYnmmCrdGQN7J7GuASJl2g9ADcFTp31uSE47+70QD86XQSpQUQfraPKKr0wiZiSn0+wWxeFKGm8XCIyh5lZmzrL3vBrPKB2lsJov82UXfJ2JXw5Pd5MsFwCVp2bbVWiXBHzYk//NjGVtuxkMbxdFATtAQqjTVMwEFDGR14= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788350261; c=relaxed/simple; bh=/uVVaZbANKTyQZBvzqokqiJ5S0l7q5Ev2Sa3zWB4nwQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=dawOSMYXc347wVJZjCt3/iXWCXYMc66SmbtK8ifFeJGI5we5A+LeSlf4oWLP5UhfLEW9aNHrQuj5OW+4uKMCuSYYY5cLEZQPiyC3o3/9sEbwc0ebyOp8cobKzvpSHrn0CtBUS16eRjPfpDalF5w7kLWv56CBEL1lLKf99Qi+Y/A= 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=jWEeau8t; 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="jWEeau8t" 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 6CE5A1D70; Wed, 2 Sep 2026 04:57:24 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 15A5D3F85F; Wed, 2 Sep 2026 04:57:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788350248; bh=/uVVaZbANKTyQZBvzqokqiJ5S0l7q5Ev2Sa3zWB4nwQ=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=jWEeau8tzvvOEJXMajlw0s2Og1QbQrAamo2x7HYqtmKGW5bh/GYdN4OCHuQHZowYN TmKaih9bsJcgin/v5UhXkmHL/FyORMqpa6csnzF80NXkHtZQUA9VuB56RP2EVvumeQ M4gDZeFItRFdcWxnkaj++wrQeFU39j68RwDt1bvg= From: Yeoreum Yun Date: Wed, 02 Sep 2026 12:56:09 +0100 Subject: [PATCH RFC v3 07/21] mm/pgtable: define (pgd|p4d|pud)_offset_lockless() for folded page tables Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260902-dummy_ptxp3-v3-7-5d8f5b17c25c@arm.com> References: <20260902-dummy_ptxp3-v3-0-5d8f5b17c25c@arm.com> In-Reply-To: <20260902-dummy_ptxp3-v3-0-5d8f5b17c25c@arm.com> To: Russell King , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , Catalin Marinas , Will Deacon , Arnd Bergmann , Andrew Morton , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , David Hildenbrand , Michal Hocko , Lorenzo Stoakes , Tianrui Zhao , Bibo Mao , Anup Patel , Atish Patra , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonas Bonn , Stefan Kristiansson , Stafford Horne Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-openrisc@vger.kernel.org X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4358; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=0K77KUA2sW2O3loVo0xQJvE1O+c56uuIFMZeynwrGG8=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqmA7lnvBstmPeoa+tQW6jXHQCdviCtwcFUASWP PwH1pn6cH6JAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCapgO5QAKCRBt1cPRWsUx M2EoC/4spxeicYhe0dGTJBcXGHGvIvetXBxvYCenurnv2K7/veM+Hixfu6V0L9cF33kWA78aSzf +ldUT24g+izjNf9DXOWjwMtW0cvqMzLAMSI+t6g8b42alZPRJhOk8LR0GdTww3EAbQXrglpcvqs Sv0yfLpVt9bEglmkJrbozEiK+WPhQ5tyqEELuq/yAH8TjnE2uZ7fvf13Kj5amZMbeZKG7k/IxQP CtxvwBUmgwlVmv3wYaGogz4sRZPEUjaYdrmeC1gNdaYx6j4IW6mjBY2LHpqeV9LwejE2GRX63OX TDhnYfZiH7LLWACLvTjUnxbvziGFz9gQ1tBpjGyuBmxRWG8kQpxz1lRq8qJ9+9d/FxwVz5BU7Wf 0jhfHnh95KL9JJ86YJ/+cq2H+uZJsZoSm3El/g83fGpqw5bqzDHu6TJODSjEvCbrTAPYynWqR1V QwdXl1hJ9cfSbbMxQJGhEQpCGDgEji8BP+ZQy7i+uIHtXdd2fJUd10EyagGmlCXLGttjs= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 From: "David Hildenbrand (Arm)" The default helpers fallback to pud_offset(), passing a pointer to the stack value. Let's provide variants that do exactly what (pgd|p4d|pud)_offset() do, but ignore the passed pgd_t/p4d_t/pud_t, consequently not working on a pointer to the stack value like the default handlers would. With this patch, Drop the arm64 custom variant that did that. As it documents: Note: reusing the original pointer means that it may be dereferenced the same (live) page-table entry multiple times. This is safe because it is still only loaded once in the context of each level and the CPU guarantees same-address read-after-read ordering. Do not document this, as the double read will be removed in the next patch. Signed-off-by: David Hildenbrand (Arm) --- arch/arm64/include/asm/pgtable.h | 23 ----------------------- include/asm-generic/pgtable-nop4d.h | 7 +++++++ include/asm-generic/pgtable-nopmd.h | 7 +++++++ include/asm-generic/pgtable-nopud.h | 7 +++++++ 4 files changed, 21 insertions(+), 23 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index e89ec5f4787b..a3c882e46777 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1180,29 +1180,6 @@ static inline bool pgtable_l5_enabled(void) { return false; } #define p4d_clear_fixmap() #define p4d_offset_kimg(dir,addr) ((p4d_t *)dir) - -static inline -p4d_t *p4d_offset_lockless_folded(pgd_t *pgdp, pgd_t pgd, unsigned long addr) -{ - /* - * With runtime folding of the pud, pud_offset_lockless() passes - * the 'pgd_t *' we return here to p4d_to_folded_pud(), which - * will offset the pointer assuming that it points into - * a page-table page. However, the fast GUP path passes us a - * pgd_t allocated on the stack and so we must use the original - * pointer in 'pgdp' to construct the p4d pointer instead of - * using the generic p4d_offset_lockless() implementation. - * - * Note: reusing the original pointer means that we may - * dereference the same (live) page-table entry multiple times. - * This is safe because it is still only loaded once in the - * context of each level and the CPU guarantees same-address - * read-after-read ordering. - */ - return p4d_offset(pgdp, addr); -} -#define p4d_offset_lockless p4d_offset_lockless_folded - #endif /* CONFIG_PGTABLE_LEVELS > 4 */ #define pgd_set_fixmap(addr) ((pgd_t *)set_fixmap_offset(FIX_PGD, addr)) diff --git a/include/asm-generic/pgtable-nop4d.h b/include/asm-generic/pgtable-nop4d.h index c6a5a43899b5..019c3f074b77 100644 --- a/include/asm-generic/pgtable-nop4d.h +++ b/include/asm-generic/pgtable-nop4d.h @@ -39,6 +39,13 @@ static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address) return (p4d_t *)pgd; } +static inline p4d_t *p4d_offset_lockless(pgd_t *pgdp, pgd_t pgd, + unsigned long address) +{ + return (p4d_t *)pgdp; +} +#define p4d_offset_lockless p4d_offset_lockless + #define p4d_val(x) (pgd_val((x).pgd)) #define __p4d(x) ((p4d_t) { __pgd(x) }) diff --git a/include/asm-generic/pgtable-nopmd.h b/include/asm-generic/pgtable-nopmd.h index 4e5aaf253b6a..1dd5b165234b 100644 --- a/include/asm-generic/pgtable-nopmd.h +++ b/include/asm-generic/pgtable-nopmd.h @@ -49,6 +49,13 @@ static inline pmd_t * pmd_offset(pud_t * pud, unsigned long address) } #define pmd_offset pmd_offset +static inline pmd_t *pmd_offset_lockless(pud_t *pudp, pud_t pud, + unsigned long address) +{ + return (pmd_t *)pudp; +} +#define pmd_offset_lockless pmd_offset_lockless + #define pmd_val(x) (pud_val((x).pud)) #define __pmd(x) ((pmd_t) { __pud(x) } ) diff --git a/include/asm-generic/pgtable-nopud.h b/include/asm-generic/pgtable-nopud.h index 6c9bca78047c..5a2b0a81ae19 100644 --- a/include/asm-generic/pgtable-nopud.h +++ b/include/asm-generic/pgtable-nopud.h @@ -47,6 +47,13 @@ static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address) } #define pud_offset pud_offset +static inline pud_t *pud_offset_lockless(p4d_t *p4dp, p4d_t p4d, + unsigned long address) +{ + return (pud_t *)p4dp; +} +#define pud_offset_lockless pud_offset_lockless + #define pud_val(x) (p4d_val((x).p4d)) #define __pud(x) ((pud_t) { __p4d(x) }) -- 2.43.0