From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BF7461073CA5 for ; Wed, 8 Apr 2026 12:13:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=H5ScxPBx0kg7ANwrTp5zjzec2BzFmHNH/iCqb6c5JzU=; b=pjEKFR+54X60r3MvIH+3eqowaB 1yn70a3wud9dSc0w5B0BFsWKgJhk05RkFQHsJPRLkEoDmESgo01S94yZPHEHYq1O69YnxS+aabr7Z DCNj3uLksmLGnzRUcfQ6Xaje/g18ThS/XpwgPBhIbMfoBugeVl2qnI9UrPutp2dW5EqrWGAjntfqq uT3F3Zf5e5uaV7XVhsBpPIh/mr6jsRYsEG3SIHF8k49Af8ObGKSKpNTThLAZoW0XV9o+wSTdyiuQW 60a5VaGo9xgioSGRe6eZr5VNyAj1KozvLTHnMPsA4lDQ7ujyNfRPdk49A/67+DhL0MD3l/cmqdZT+ O2+Yta8g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wARmy-00000008nqW-0BGI; Wed, 08 Apr 2026 12:13:44 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wARmw-00000008npt-26ve for linux-arm-kernel@lists.infradead.org; Wed, 08 Apr 2026 12:13:43 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 2E54E40521; Wed, 8 Apr 2026 12:13:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B26D2C19424; Wed, 8 Apr 2026 12:13:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775650422; bh=My9ex2aNfAQr85RMj/PNNceXRhuE1pGC/rvjjhvlKho=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=fm4pYk+i6DilsXsT+t8GY4iXYWcW035fNURZeBfTqXB9B2RHLiHuFxqigp1rueLf2 IGKW4LWsJv2ucGAUoKuh2azO8SS5Wre66FjKiCABx/HucXfyegCmGc9lzI6vXZm9TK IRIn/uNZIhUCkHmI5GvnB0izbKU55WHY8/qhSYDgLF+SJ/S2EgfLoWg9Cy++NZmfVV zBhwO2uVX1GHHK9yz42oCR5YFqm6oBIxDibRsv1V8zutdmVYIKkkil68x+IhfAdKQ3 G2j6eq6FwzrPCG9IfEdd/fZKO+YrDfABRPtn4RywDcud+oDOGYsONZgdcI5cfhD47D KWN2m7RrTEYHg== Message-ID: Date: Wed, 8 Apr 2026 14:13:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC V1 00/16] arm64/mm: Enable 128 bit page table entries To: Anshuman Khandual , 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 References: <20260224051153.3150613-1-anshuman.khandual@arm.com> <8d2c9ecb-ae33-42f2-a8ed-66b3286b9286@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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260408_051342_587763_934FF87E X-CRM114-Status: GOOD ( 14.84 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 4/8/26 12:53, Anshuman Khandual wrote: > On 07/04/26 8:14 PM, David Hildenbrand (Arm) wrote: >> On 2/24/26 06:11, Anshuman Khandual wrote: >>> FEAT_D128 is a new arm architecture feature adding support for VMSAv9-128 >>> translation system. FEAT_D128 is an optional feature from ARMV9.3 onwards. >>> So with this feature arm64 platforms could have two different translation >>> systems, VMSAv8-64 and VMSAv9-128 could selectively be enabled. >>> >>> FEAT_D128 adds 128 bit page table entries, thus supporting larger physical >>> and virtual address range while also expanding available room for more MMU >>> management feature bits both for HW and SW. >>> >>> This series has been split into two parts. Generic MM changes followed by >>> arm64 platform changes, finally enabling D128 with a new config ARM64_D128. >>> >>> READ_ONCE() on page table entries get routed via level specific pxdp_get() >>> helpers which platforms could then override when required. These accessors >>> on arm64 platform help in ensuring page table accesses are performed in an >>> atomic manner while reading 128 bit page table entries. >>> >>> All ARM64_VA_BITS and ARM64_PA_BITS combinations for all page sizes are now >>> supported both on D64 and D128 translation regimes. Although new 56 bits VA >>> space is not yet supported. Similarly FEAT_D128 skip level is not supported >>> currently. >>> >>> Basic page table geometry has been changed with D128 as there are now fewer >>> entries per level. Please refer to the following table for leaf entry sizes >>> >>> D64 D128 >>> ------------------------------------------------ >>> | PAGE_SIZE | PMD | PUD | PMD | PUD | >>> -----------------------------|-----------------| >>> | 4K | 2M | 1G | 1M | 256M | >>> | 16K | 32M | 64G | 16M | 16G | >>> | 64K | 512M | 4T | 256M | 1T | >>> ------------------------------------------------ >>> >> >> Interesting. That means user space will have it even harder to optimize >> for THP sizes. >> >> What's the effect on cont-pte? Do they still span the same number of >> entries and there is effectively no change? > > The numbers are the same for 4K base page size but will need > some changes for 16K and 64K base page sizes. Something that > git missed in this series, will fix it. Oh, and it would be great to also clearly spell out the effect on hugetlb as well. I assume the available hugetlb sizes will change as well. -- Cheers, David