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 1DB81EA7943 for ; Wed, 4 Feb 2026 20:47:32 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6179B6B0005; Wed, 4 Feb 2026 15:47:32 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5D5516B0092; Wed, 4 Feb 2026 15:47:32 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4D7896B0093; Wed, 4 Feb 2026 15:47:32 -0500 (EST) 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 393A96B0005 for ; Wed, 4 Feb 2026 15:47:32 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id B3B6B1C15A for ; Wed, 4 Feb 2026 20:47:31 +0000 (UTC) X-FDA: 84407959902.06.288963B Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf14.hostedemail.com (Postfix) with ESMTP id EEEFA100014 for ; Wed, 4 Feb 2026 20:47:29 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ceImbz8E; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 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=1770238050; 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=JE9K9cnxHEioD0bY/0SBJmhMUUNEI8hO7Ksv7scdRCc=; b=IT+W6HTVXfVCXrxNBbuevZ56CsvPFXP2MUKrpvrMmhf87sDmMlEV+F13Y0etXpa1E6qRLL 40Cx5BDMqHykvcJ+TiYeM/Ah+ujVcRWB7xuxmh1iA8glfsGAU6SbezZbq6KilDjspsHj7e 4KlVXkZAOFMj+Bwzj9z+XWqXdaLjY1o= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ceImbz8E; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1770238050; a=rsa-sha256; cv=none; b=1+CrnEr71C4ExkQI74kefxrv6mxF6BAtPT16q2gtn1Cw0rOUYwdEhmsEuIAhGWFWJ34RHM pvF+8tvRLPTOfTzrOKcGDyda9FlqYo9vCQ5iJoM7azv7eCss33PSTRsXRQhZv9v/gGwaeM 5eNhOMrZd/8hmRZzwzPa3Q7L8brGiYY= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 591C560010; Wed, 4 Feb 2026 20:47:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD6EFC4CEF7; Wed, 4 Feb 2026 20:47:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770238049; bh=M6F4r+8xqCKwYdWkmNuqBBLFmaH1X62wessV5kAOjaY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ceImbz8Ehfv99L+KpKZmE6O02UITPIW3Q3unzHK6ZvZ03KKVV9vd0o/zcMuSR8I/T H1Ir3pkRy/Ac8NihhmQc2XLTMSvLY7g8u6dkzpUWxLGR59JnhG3WFIY+0sjN6+ny7L OA5yX5VUcxDkJ35fbSlJkf7gZPNX9n4UDZ49V6CXYwaJng3pK5jMKjC8bZQ49jWrDJ mh81ww5c4mKrrXjIQs9nNyAtjUxe+jiJJyDGCyhHXV8PWeMF/uLi6iv05wTvaTDa01 /w1na7IgsBIyj8KXiazPHDVq2pFYUxDfVF0755O+BReCpOPHi91jybdC/Nf+ItlP65 sGqFAAkbH50Hw== Message-ID: <36511161-6fb0-4928-a0ed-9b5e03b50a27@kernel.org> Date: Wed, 4 Feb 2026 21:47:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable] arch, mm: consolidate empty_zero_page To: Mike Rapoport , Andrew Morton Cc: Andreas Larsson , Borislav Petkov , Brian Cain , Catalin Marinas , "David S. Miller" , Dave Hansen , Dinh Nguyen , Geert Uytterhoeven , Guo Ren , Helge Deller , Huacai Chen , Ingo Molnar , Johannes Berg , John Paul Adrian Glaubitz , "Liam R. Howlett" , Lorenzo Stoakes , Madhavan Srinivasan , Magnus Lindholm , Matt Turner , Max Filippov , Michael Ellerman , Michal Hocko , Michal Simek , Palmer Dabbelt , Richard Weinberger , Russell King , Stafford Horne , Suren Baghdasaryan , Thomas Gleixner , Vineet Gupta , Vlastimil Babka , Will Deacon , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-mm@kvack.org, x86@kernel.org References: <20260124095628.668870-1-rppt@kernel.org> 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: <20260124095628.668870-1-rppt@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: EEEFA100014 X-Stat-Signature: pdkg5471czcjhxii17izt8h516ioxaaz X-Rspam-User: X-HE-Tag: 1770238049-648711 X-HE-Meta: U2FsdGVkX18Xx5ZSEjBtRTdArk1WQnY+GdBGjJ0yYIrZEKVPx1MxLjRM9kluXa5v/4THd4Sjz7ZNqMvdLmaQAqWDAWLV9NglqhVYYcZEnfg7vUrtvj3ifMrzkP8F6v4/AeRKmF4xmZknrvveQXkkYPN9Qsm33AppnrD3GiumeTqc7U+7VS1MKdOEcQ9TFw/3facT9IiGjYEPfCu2T5CNP/kWuuJvDYhZBDSv0aCv+MVdkkhRGiv9/sSxAeRXd5ctTVMnwRzB7UvacJZC/HeWwiTEKqu639k52XvueJgqSYpmAIscEYy4fnqsqdmdo8w7RQwgn82sS2AMwF9lEavZdm50CU3SSNU3S/0FBqC1Hwh/5zZm3dooQ0K1esuQ8Om0ksQdACRgmJ7Wv12looAw4ldqpxIN3cO2UTC+bkDwCMpDPbExW5kCNyDLmR12yhj6Mm0tAzO94rcgwjRLc2f5ARp9DuQeNJm592R7ribdUDJa8/9TxXilynQFuvPgFR+MSgZngab9dfHnRFUtyg94myDVhbdaKMM9sRK2XCByKSNGQqotGJ0rJjE8aqrmPMdHlJeJzBlb2g1eZ7WiNTBEtznbuKJc+wteHPuuyq4xKAWAXdjVlLQ0Q05sO8hAUjcLaOfl1dVD7X8suK7U+kBnz0ZZ5nV8pcYfzrFb49CjH0JwhVV5Mq8wObjPtVlu7yj+V5dAsFe0y/2PB9/qNoyj7kk3ZKcTuJ3o28cEyt/padkZfDl4CqJCTSfhAJ/DPTlBakwRa18AmQJDh46gM+/KrcLcE30gDvCPx4WcFgQ7XkvrNVUP84QQ49m0+88zQkiaziGeGYOGOALLGvqdn7BfzkNH1Ib3SW2hq/wf6uf2Q6zoz+teLIVS2RTVA1N/oGnti4fnF4NiL7P0R5B9RQyCl8g6gA4LI1r/5LgSXBZJDUae6ygPnqxd4p2HHOBFrYn9o7uP/RKJ6RSrvVWMulk 7Gg0B7fT lWnhpq3z0tSRoYF2LuxnB1xD8IOJhFbS+GgMSzXBgMGltsoE43vXwo+KwxjZe86JRlqBYlpX0HYnpCYpOq1SxU76l1YJ8BEH2/79xnU01DcOpLPnF2kcOVFrRAaCqnH1O95/pOXZXv+EU01QGWxdZ8VT0nIXN5nXfIOIRXng7YYjKcjxuVdkJU+omNONTcFRV7ZqBamnNTqH5jVFFrWyYy6DY+whcfyYBjLDvc/PUJgJWjvy7sHCAo6NAmPfoK9BdBxLdEDVKTbna+cR9D+6ol7S7Kcs86beD+0UmGLhwEegJVe93YUX4xP97qK6ZAw+dN7EDgRK3q0etpBA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/24/26 10:56, Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" > > Reduce 22 declarations of empty_zero_page to 3 and 23 declarations of > ZERO_PAGE() to 4. > > Every architecture defines empty_zero_page that way or another, but for the > most of them it is always a page aligned page in BSS and most definitions > of ZERO_PAGE do virt_to_page(empty_zero_page). > > Move Linus vetted x86 definition of empty_zero_page and ZERO_PAGE() to the > core MM and drop these definitions in architectures that do not implement > colored zero page (MIPS and s390). > > ZERO_PAGE() remains a macro because turning it to a wrapper for a static > inline causes severe pain in header dependencies. That's just what I wanted to ask after looking at it :) > > For the most part the change is mechanical, with these being noteworthy: > > * alpha: aliased empty_zero_page with ZERO_PGE that was also used for boot > parameters. Switching to a generic empty_zero_page removes the aliasing > and keeps ZERO_PGE for boot parameters only > * arm64: uses __pa_symbol() in ZERO_PAGE() so that definition of > ZERO_PAGE() is kept intact. > * m68k/parisc/sparc64/um: allocated empty_zero_page from memblock, > although they do not support zero page coloring and having it in BSS > will work fine. > * sh: used empty_zero_page for boot parameters at the very early boot. > Rename the parameters page to boot_params_page and let sh use the generic > empty_zero_page. > * hexagon: had an amusing comment about empty_zero_page > > /* A handy thing to have if one has the RAM. Declared in head.S */ > > that unfortunately had to go :) > > Signed-off-by: Mike Rapoport (Microsoft) [...] > > +#ifndef __HAVE_COLOR_ZERO_PAGE > +extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; > +#endif > + > +#ifndef ZERO_PAGE > +#define ZERO_PAGE(vaddr) ((void)(vaddr),virt_to_page(empty_zero_page)) Took me a second ... > +#endif > + > #endif /* !__ASSEMBLY__ */ > > #if !defined(MAX_POSSIBLE_PHYSMEM_BITS) && !defined(CONFIG_64BIT) > diff --git a/mm/mm_init.c b/mm/mm_init.c > index 1a29a719af58..8ea5b76f317f 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -53,6 +53,15 @@ EXPORT_SYMBOL(mem_map); > void *high_memory; > EXPORT_SYMBOL(high_memory); > > +#ifndef __HAVE_COLOR_ZERO_PAGE > +/* > + * ZERO_PAGE is a global shared page that is always zero: used > + * for zero-mapped memory areas etc.. > + */ I am not so sure of how much value that comment here is. ... and in particular, why it is not next to ZERO_PAGE in pgtable.h? ;) > +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; Is there a good (or historic) reason why this is not simply uint8_t empty_zero_page[PAGE_SIZE] __page_aligned_bss; Almost looks to simple, right? So there must be some problem with it :) > +EXPORT_SYMBOL(empty_zero_page); > +#endif Nothing else jumped at me, nice cleanup ... if you get sparc to work :P -- Cheers, David