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 83D5ACA0FED for ; Wed, 10 Sep 2025 19:37:50 +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:MIME-Version:Subject:References:In-Reply-To:Message-ID:Cc:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Kvy79l38OjgXam56LG4SBUALLkxIDxyLLpk0bImYB5k=; b=JEO12C1XEqEx98slJHUBH1GPiZ yd5UtMCrxRlzwnnwIVVMO5HMcBmPOyD2xxlbshrEFocIbFdFdkz31L5+rRAjf+J4kjtLKTSenIRNT ESC+VlLYbhhcO9om9zvLFDYMfejJZxsF9czdZlwcIcZTcc4ytN2HL6VWSnxkps2P8iiv0ep1tQVpy z850sCVSMSROlwR4dZA+tZ8PIoPgTAXeO5NdcJwfQrIsJkLqB//5UDs/QObu3eGYiEbqiOQbG/JLT udWDmry7bBgpnbR+WwpHXWRIumT1k41/LqTLqY5s4TWhM9Kvg+axAYNlydv0C0lp8BwXXFr0g8mR3 RxLj0y0A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwQdV-0000000GLad-18fN; Wed, 10 Sep 2025 19:37:45 +0000 Received: from mailout.nod.at ([116.203.167.152] helo=lithops.sigma-star.at) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uwQdS-0000000GLYT-11ap for linux-arm-kernel@lists.infradead.org; Wed, 10 Sep 2025 19:37:44 +0000 Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id E33972C14AA; Wed, 10 Sep 2025 21:37:38 +0200 (CEST) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id mZ4QcxbfF_Ic; Wed, 10 Sep 2025 21:37:38 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by lithops.sigma-star.at (Postfix) with ESMTP id 274732BA98D; Wed, 10 Sep 2025 21:37:38 +0200 (CEST) Received: from lithops.sigma-star.at ([127.0.0.1]) by localhost (lithops.sigma-star.at [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id Q1j44iMB0ybE; Wed, 10 Sep 2025 21:37:38 +0200 (CEST) Received: from lithops.sigma-star.at (lithops.sigma-star.at [195.201.40.130]) by lithops.sigma-star.at (Postfix) with ESMTP id D9D02CE340; Wed, 10 Sep 2025 21:37:37 +0200 (CEST) Date: Wed, 10 Sep 2025 21:37:37 +0200 (CEST) From: Richard Weinberger To: Christophe Leroy Cc: Arnd Bergmann , ksummit , linux-kernel , linux-arm-kernel , linuxppc-dev , linux-mips , linux-mm , imx , Lucas Stach , Linus Walleij , Geert Uytterhoeven , Ankur Arora , David Hildenbrand , Mike Rapoport , Lorenzo Stoakes , Matthew Wilcox , Andrew Morton , "Liam R. Howlett" , vbabka , Suren Baghdasaryan , Ira Weiny , Nishanth Menon , heiko , Alexander Sverdlin , "Chester A. Unal" , Sergio Paracuellos , Andreas Larsson Message-ID: <1586788245.22320.1757533057730.JavaMail.zimbra@nod.at> In-Reply-To: References: <4ff89b72-03ff-4447-9d21-dd6a5fe1550f@app.fastmail.com> <497308537.21756.1757513073548.JavaMail.zimbra@nod.at> Subject: Re: [TECH TOPIC] Reaching consensus on CONFIG_HIGHMEM phaseout MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [195.201.40.130] X-Mailer: Zimbra 8.8.12_GA_3807 (ZimbraWebClient - FF141 (Linux)/8.8.12_GA_3809) Thread-Topic: Reaching consensus on CONFIG_HIGHMEM phaseout Thread-Index: BY4xIXfJeETYMNF0Cnq/68k1mYFqTg== X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250910_123742_426072_5814DA62 X-CRM114-Status: GOOD ( 12.63 ) 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 Christophe, ----- Urspr=C3=BCngliche Mail ----- > Von: "Christophe Leroy" > Can you tell which PPC32 model/family you are using ? Is it mpc85xx or > and/or other variants ? Maybe we can look at keeping CONFIG_HIGHMEM or > find alternatives for that subset of PPC32 only. Off the head, MPC8343 and QorIQ P1022. >=20 > Could you also elaborate a bit on the kind of issues you forsee or fear > with applications and FPGA device drivers. Unfortunately, applications in this area often make certain assumptions about the amount or layout of memory. This becomes a bigger problem when using FPGA device drivers of questionable quality, which share memory between the kernel, userspace, and the device itself. These are mostly out-of-tree drivers, so that's my horse to ride,=20 I'm just mentally preparing myself for "interesting" bugs that will need to be sorted out. > FWIW I sent out today a patch that removes CONFIG_HIGHMEM complely on > powerpc in order to get a better view of the impacted areas and allow > people to test what it looks like on their system without > CONFIG_HIGHMEM. See [1]. Oh, that was fast. :-) Thanks, //richard