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 38A512E7BD6 for ; Fri, 10 Apr 2026 05:30:32 +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=1775799033; cv=none; b=q3OGC2lp+nRaz5rPZbEG20cxl90DA2hZ1ciX0/SrsPLTU2cPSavG9uU6fbO72wKd74Dm6ibvKdzrjFPNVWxIk2PMeiY8GvTKKyU5hN1Iz8fdYTwHwt1AsR94wKW/AitAGB7FRlKJZS2v3WnayxJpCsLEB9RXxf+eHAyaBW+kdq0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775799033; c=relaxed/simple; bh=G8k+wf8sxRtAbSVAFMjynOWx4nhCOUiQl5JR82uclTA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=asfTJeml0N27YLw77jOlPhbYW/QeJA35bTrJj/MzgWIPaeENRzivI7zmVjIv598rgNbFD/BOiVOEQfppbPXz6SW55slYOJgV5gILd2tjKoZHYYiJfPLvD+LJQa3mOQugC1OA48hxlSZcMg2rwPnJ9+cACYDcaw1zH8EytQn6Duc= 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=pAgcGKUF; 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="pAgcGKUF" 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 D84282008; Thu, 9 Apr 2026 22:30:25 -0700 (PDT) Received: from [10.163.181.174] (unknown [10.163.181.174]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DAFD53FAF5; Thu, 9 Apr 2026 22:30:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1775799031; bh=G8k+wf8sxRtAbSVAFMjynOWx4nhCOUiQl5JR82uclTA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=pAgcGKUFPcmqcSGKzUfH7nLwJKsdSljWyGBHIdKx+8b8fUDXYywKAnnv1cjrSYsiG Ertxa4ZqReOgzsGxkJsZrto/EoLahijks7RmJHy2Ou97NaTkJN7j4K59/bLN7zdhkd 6/RmOE3X3nlyjferzBy6Ln/oVRuJLouqFvEzMRto= Message-ID: <37a7e502-ac1d-4573-a877-23b1bfd07238@arm.com> Date: Fri, 10 Apr 2026 11:00:24 +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: [RFC V1 08/16] arm64/mm: Convert READ_ONCE() as pgdp_get() while accessing PGD To: "David Hildenbrand (Arm)" , linux-arm-kernel@lists.infradead.org Cc: Catalin Marinas , Will Deacon , Ryan Roberts , Mark Rutland , Lorenzo Stoakes , Andrew Morton , Mike Rapoport , Linu Cherian , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com References: <20260224051153.3150613-1-anshuman.khandual@arm.com> <20260224051153.3150613-9-anshuman.khandual@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 08/04/26 5:49 PM, David Hildenbrand (Arm) wrote: > On 2/24/26 06:11, Anshuman Khandual wrote: >> Convert all READ_ONCE() based PGD accesses as pgdp_get() instead which will >> support both D64 and D128 translation regime going forward. > > Please mention here why you move p4d_offset_phys/p4d_offset. (same > applies to other patches) Will do that. > > Do we get additional function calls that might degrade some page table > walkers? Sorry did not get it. Are you asking if D128 adds new page table function paths thus increasing memory access latency etc ? > > Same comment regarding BUG_ON. > As mentioned earlier it might be better to have a separate change converting similar BUG_ON() in various arm64 page table helpers.