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 3FD97360EC4 for ; Mon, 7 Sep 2026 15:48:23 +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=1788796105; cv=none; b=vAcT76cIPbdDvZPi4We3XcmHWW/iqO7HnfOKHsDWQY5iF+/wMgtOnSNPxbvD7a+tVnLRVaUEUpBlOkcqEeGsUgUEMkbovqQPNJ+E5o7eHQbn+2CWMwKdjaHSf+THjBOpmZ6XEFuN82+zAG8gA5yShHjQggxgGctCZiizxbpsp3g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788796105; c=relaxed/simple; bh=2pTswNwhgqiX1W184B9qLTYxtwrLzIjtMGsuHgzr/Mk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SYYDSSm1KidnbviYCto2/A4jExONOx1GqUidUd5HhjseXpXiEZ4YFxI/ka927mS46V3X4ldzPL+BXuxT/z1kVNilskhxPbkNQYKyKd8r2Bwy3fw52Zp0tUqDwcJX09YNEl/XBgstR+sJF/hq26J6UYTQtLQaQjQmH6jNvEBbYS0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lvRgPSgW; 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="lvRgPSgW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D49511F00A3A; Mon, 7 Sep 2026 15:48:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788796103; bh=wudceGLt62w3o+e3x4RUDMN4HluyPL4Ts+Eyk51ebws=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=lvRgPSgWAAdN4XQw3S2/yhtgm0ggA1Q019dIjUOymiLlfLatsBScYcJK0x4hRnETH /X8BeaWqBDCvY6Ng491iOaK7eJxS59eif9JSxCiMe/1sgAwo1jFVyGgKzFOPPHhXOu 9i6WyIW7f38b0Ddk67DZf7k+ECYL56wURose3Z6R5rjbSXl8qiCjTz0TpTKWdxOQZZ 0YTgIoHyvDcO5QgY447FEjSFduoYtWOExqC8LN9WmgoqcEUbNO4o+LTQyT690uejUV WzhTf/ZzWSJkdbOIH0xq131qlWB8m3G9ePzyg/RuD1N8DMbxrFuNLZI62jZbrOUvHP V7d5MRGyYWJJQ== Message-ID: Date: Mon, 7 Sep 2026 17:48:18 +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 1/2] arm64/mm: Move __check_safe_pte_update() To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: Mike Rapoport , Andrew Morton , Lorenzo Stoakes , Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260901065454.1906343-1-anshuman.khandual@arm.com> <20260901065454.1906343-2-anshuman.khandual@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 9/1/26 08:54, Anshuman Khandual wrote: > The page table entry print helpers and related macros which are defined in > will not be accessible in platform which > is basically caused by cycling dependency. > > Move __check_safe_pte_update() inside arch/arm64/mm/mmu.c as a preparation > for subsequent usage of the afore mentioned generic MM helpers. > > This does not cause any functional change. > > Cc: Catalin Marinas > Cc: Will Deacon > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual > --- > Should __check_safe_pte_update() be wrapped in #ifdef CONFIG_DEBUG_VM > along with dropping off current IS_ENABLED() test. That would ensure > the function never gets called when CONFIG_DEBUG_VM is disabled. That > will preserve current behaviour as the inline function gets dropped > when CONFIG_DEBUG_VM remains disabled. > > arch/arm64/include/asm/pgtable.h | 47 +------------------------------- > arch/arm64/mm/mmu.c | 45 ++++++++++++++++++++++++++++++ > 2 files changed, 46 insertions(+), 46 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index e89ec5f4787b..61fbfab3e06e 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -387,52 +387,7 @@ static inline pte_t __ptep_get(pte_t *ptep) > extern void __sync_icache_dcache(pte_t pteval); > bool pgattr_change_is_safe(pteval_t old, pteval_t new); > > -/* > - * PTE bits configuration in the presence of hardware Dirty Bit Management > - * (PTE_WRITE == PTE_DBM): > - * > - * Dirty Writable | PTE_RDONLY PTE_WRITE PTE_DIRTY (sw) > - * 0 0 | 1 0 0 > - * 0 1 | 1 1 0 > - * 1 0 | 1 0 1 > - * 1 1 | 0 1 x > - * > - * When hardware DBM is not present, the software PTE_DIRTY bit is updated via > - * the page fault mechanism. Checking the dirty status of a pte becomes: > - * > - * PTE_DIRTY || (PTE_WRITE && !PTE_RDONLY) > - */ > - > -static inline void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, > - pte_t pte) > -{ > - pte_t old_pte; > - > - if (!IS_ENABLED(CONFIG_DEBUG_VM)) > - return; > - > - old_pte = __ptep_get(ptep); > - > - if (!pte_valid(old_pte) || !pte_valid(pte)) > - return; > - if (mm != current->active_mm && atomic_read(&mm->mm_users) <= 1) > - return; > - > - /* > - * Check for potential race with hardware updates of the pte > - * (__ptep_set_access_flags safely changes valid ptes without going > - * through an invalid entry). > - */ > - VM_WARN_ONCE(!pte_young(pte), > - "%s: racy access flag clearing: 0x%016llx -> 0x%016llx", > - __func__, pte_val(old_pte), pte_val(pte)); > - VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte), > - "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx", > - __func__, pte_val(old_pte), pte_val(pte)); > - VM_WARN_ONCE(!pgattr_change_is_safe(pte_val(old_pte), pte_val(pte)), > - "%s: unsafe attribute change: 0x%016llx -> 0x%016llx", > - __func__, pte_val(old_pte), pte_val(pte)); > -} > +void __check_safe_pte_update(struct mm_struct *mm, pte_t *ptep, pte_t pte); > That implies that any __set_ptes_anysz() will invoke another function call that will not be optimized out. You should likely keep most of __check_safe_pte_update() in the header as an inline function (or at least the CONFIG_DEBUG_VM check), and only move the "slow path" code. Alternatively, make the whole thing #ifdef CONFIG_DEBUG_VM and provide an empty inline helper for !CONFIG_DEBUG_VM. That's probably the cleanest, because performance with CONFIG_DEBUG_VM is not really relevant. -- Cheers, David