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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3A799C982D2 for ; Thu, 17 Sep 2026 18:28:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2C00B6B008C; Thu, 17 Sep 2026 14:28:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2894E6B0092; Thu, 17 Sep 2026 14:28:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 160456B0093; Thu, 17 Sep 2026 14:28:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id E3EF06B008C for ; Thu, 17 Sep 2026 14:28:24 -0400 (EDT) Received: from smtpin05.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id E41971A0433 for ; Thu, 17 Sep 2026 18:28:21 +0000 (UTC) X-FDA: 85224089202.05.432413B Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf10.hostedemail.com (Postfix) with ESMTP id 0B57FC000C for ; Thu, 17 Sep 2026 18:28:19 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="hx4f6/Jv"; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789669700; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=b5zVLhEkKOWEwakOfls77zzn3VcbclTffxYn4L85i8c=; b=J1myLX1+mzIuv6fdttmMNWokugRLF8qyd8HJj4gd+Zy3/qtdnrc+qfANOWjCG21Illnwe4 w+zYCRwqfXElI7F5W00kHFi7quht/z5AOQ2shcrmOPbZdmeWVo6o9ECfVhnssc8mobV5fc MgdCAG8pZeY0uvCrr7HgDfA9iquBIKE= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b="hx4f6/Jv"; spf=pass (imf10.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789669700; b=rwAtCDNDJ1K0fIyDtREdezxH+pR+7zz2TNpFRthbmBC/hyd5UpGuDSC34T29Uedimes6pK 3AqFmvG/cv6X0tYEa08Rzr/S+/UBp+td5aej9HiEKUpndL8JrB43OcTvBL0HqPR0uA03wg WjL/yOjTjDzZpbxs8uLXZBVeYzJiAsE= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0FFF6435A7; Thu, 17 Sep 2026 18:28:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4D881F000FF; Thu, 17 Sep 2026 18:28:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789669697; bh=b5zVLhEkKOWEwakOfls77zzn3VcbclTffxYn4L85i8c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hx4f6/Jv3cwrMptmmP/azM4P7NNl4TgzLMYGPYxUvgj5fA03oSL4gHfl55lsCvHTT pn5EvppKp1xmJVGJoCg35YpgKo//7RnjqDcC6S8a+5bv13BmFQXoavodtPLD14ATOC rmLLzfgKdbwPSczeH8sX7PRwlBQtwwRWVY2CYFlhqSagmfzeq2QSmTyLzn5Sn1v1ez GsYSrSrknJk0CULzb4njUW5QsatEUpC4El2M6cPUEGGYdRiyicyK7Mntpp8rww/Avk Qil1cbyfX1lJNXxc5p1cZu4mSWyl9wU4Cbmp/v2R2k2C3fUf7DbdZRhNL48WnmlEFp ySmtFZ+wMOr1w== Message-ID: Date: Thu, 17 Sep 2026 20:28:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2 06/14] arm64/mm: Enable fixmap with 5 level page table To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, 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: <20260907035030.2839978-1-anshuman.khandual@arm.com> <20260907035030.2839978-7-anshuman.khandual@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: xa3c5xnsr5iuak914binct8hjjkfuu8n X-Rspamd-Queue-Id: 0B57FC000C X-Rspamd-Server: rspam07 X-HE-Tag: 1789669699-576018 X-HE-Meta: U2FsdGVkX190aL87Y7nX39NAIrli8MDkA+5ua0F3bgwjgl3DKWCpsQBGed1qEiO3dzFpCaZG17Qts233QHOha768t15iwqmXvbAqlKtjtefvi5B19z40m3FHLjUiHsHXn/5tzWTJg60+QmGrFZI6QoxedibSZ7YB/iKVPvSsmU7Pb2aHlmJI8wrdnwz7DqaGBhZXk34pQ1xOpan3c2aUHwetKgf19iT/OVLELNvyE2mgsODo8Sok7qXQTAXvSjOFARs6yHA2eVPQ3eb1NJG54Qz+7xTJ5LOtSf/SMyohQuAWRziawqXF1wjWG3wLsZHJSwJb0DKmcyCsAHauyFJIdubYWI9pil3g21nP9+n3/XTQrQ8j45WEi6Z4SXBGMQYLtyN93i0142qxdU0QnMTYM+DRjihUtTptDrh4TgktyQGH+8OFakmwx569gFmOjLCJ9/sVtr2tTgQrfJh3S6Apk8wHTHVpkmvkxZew+RFQxxhByq6zecINW7tAp1n9JkOveJOSqSGAaz1uejackz4EDtwirCCC+bmqwZVIzMWH4DhPnhH54HmY6fBM2TnpHj2sPL1qcpMKO4ULv4xzJyDZwQ8J6XAvdUhUgu2molfzTUW969YBeVA/fLFDrmw/gT5XZsp2Qqk8GfESQhpOv/178GbKHWPqbT9kMMDLcBriydPlm/jYEq2Ohq6+XTEBmAGyvlMVF9GxMQzItQ6G319YUkT3zA8S9+lFNq4cjwDVq9UL8zpIo2XVLsQrcVsLao2KvIzjLRfX6eKFNEV+4IsJANeWBzXQ5D/0vFbk3aUFkv/PF5KBdTGXbb0SXaAxBDYAIoO5odw1bo9sGGetMWt07B2jMWncN/9dYxntyPsNX7rl1T4Hx7tY6FzO2pFNwDxInDsri0AJqrlpka5bY2XZq64zorVMOfeVbxSrUXi72aWwjOw4RkdHAIo98f4e4hv0qiNemQcoPLQSpPuA2m0 lCxxabdk 7EMW0oaGTpxAfxd3xcBAS1DrWvePF0+fcTv/rCDTxVVDZagI7Dcpy6ZfuVIUbMRuKkdZ1ofESgBfXBfufRGQwZwn/CHNlA2zipwgFnDSsbXieYwyetaegLb2DUamgXa8mkI1dUcphGLSv4HD1F0pL6rjeU7m0Cwh7cZcDmMJckcdM9IzRCaTOs9cvy8dLSZX12vOfJo5Fn1BB5ZvVZaKvd+R63ogITGnBijXsanfmopy7jU1nlMr/XSgRxya5NwBo3Qx1 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/17/26 08:18, Anshuman Khandual wrote: > On Wed, Sep 16, 2026 at 04:30:05PM +0200, David Hildenbrand (Arm) wrote: >> On 9/7/26 05:50, Anshuman Khandual wrote: >>> FEAT_D128 halves PTRS_PER_PXX thus shrinking the VA range coverage >>> for each page table level. Hence in order to preserve all existing >>> VA range configurations, some geometry now need to become 5-level. >>> >> >> Hmm, wasn't this 5-levels before, but other code allocated+initialized the p4d >> table for us? > > But fixmap was never 5 level earlier. I mean the page table hierarchy. It's confusing. > >> >> I mean, I see how we are filling in another level, but I don't see how we would >> reconfigure something to use 5 page table levels? > > IIUC existing configurations which never required 5 levels would not need > this reconfiguration even now. We only map a handful of MB into a single leaf page table. The only reason why we have to install more page tables into upper levels is because they were not instantiated by other code. > >> >>> Since fixmap is used to build and manipulate page tables early on >>> during boot the mapping must also gain that additional level which >>> was not required earlier. >> >> I am no expert ... but I am confused :) >> >> We do have a loop only in early_fixmap_init_pmd(). So we cannot possibly span >> more than a single ... PTE table? >> >>> >>> Enable fixmap with 5 level page table when required. This creates table >>> entries at the PGD level. Add a fallback stub for pgd_page_paddr() when >>> (PGTBALE_LEVELS <= 4) which helps in intercepting any unintended usage. >> >> >> Again, I am very confused. Is it really just "As the page table layout changes, >> we might no longer have a p4d table pre-populated for the range our fixmap falls >> into. So if there is no p4d table yet, populate a static one just like we do for >> the other levels." > > Right. Best to rewrite the patch description along these lines. -- Cheers, David