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 A77C2C64ED8 for ; Mon, 27 Feb 2023 16:37:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=gauEynN7ACbcItuZ0tg2rOva3ol6YtlfgZShaEOvNTM=; b=z1WVCYdt5i/VOt t+wXTxzA4YAqrNl3/pRWC65Ap6jIGpjZGbaVr43RhqTA28pqP4opEy97vn8OXzkLWO4FzihFJecXn zVa+PSobe8/DWc2yHfBUoMFjzr50fkOUzbd3vPGljMuYC/MkBiRwMvSQ4CbJZuaxZa753BgL/PAKg XRe88vz/9kHQvJQ966NHaBX2zNvCWc1X298fosVVAuBqH+7P4KogWWDfvkaBP+6vYlqQHtMu4Iai/ e5X1f8WQyMPa0DI3gsmbNI9vD+r5fVjaPEidmuYiK91zb+Q/hDm9fZsUb1XOUOUCHypgiyPQqtpcr b+QfKS+FQICRz1MM/GVA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pWgV9-00ANhZ-NR; Mon, 27 Feb 2023 16:37:23 +0000 Received: from mx.sberdevices.ru ([45.89.227.171]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pWgV6-00ANgb-EP; Mon, 27 Feb 2023 16:37:22 +0000 Received: from s-lin-edge02.sberdevices.ru (localhost [127.0.0.1]) by mx.sberdevices.ru (Postfix) with ESMTP id 1C89C5FD23; Mon, 27 Feb 2023 19:37:17 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sberdevices.ru; s=mail; t=1677515837; bh=XV8j+HbOiRy1aa6d+0JDl+RpUDnhvQ0IDo+fq+PYfjM=; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type; b=OL6DFWLWlPu1DV+ky2V9w8NQ5beb/Yd7Y5L0uQGbnq/G2l1Wy3RtMNUHPddDc7Fis VSOeJ/6XxFtbZWgMR1+Mpnh44pnyXMe9Bn5xXPEbhSm5db9STCn858yMIA4hnNthp2 iO0hdfqpiJveJbmwPkV3+XsFj2ZPIssy8U0wdIH5Z0nkkkYjrAsIS1hWkhxqvW0daR amhCsPLbOEwAFrXBsSQVEeKqNgmMPjPQL+2Fzad2CuNB7JFoXWUkivJrEU73+cWgJZ 3mqAA53SwuqPxxeh7EMNaqxlFUrM7t89r2wHA74xlRDDDufTdN+waJu+Ruuz+oec// LAr4IpAbBRa6g== Received: from S-MS-EXCH01.sberdevices.ru (S-MS-EXCH01.sberdevices.ru [172.16.1.4]) by mx.sberdevices.ru (Postfix) with ESMTP; Mon, 27 Feb 2023 19:37:16 +0300 (MSK) Date: Mon, 27 Feb 2023 19:37:16 +0300 From: Dmitry Rokosov To: Arnd Bergmann CC: Neil Armstrong , Alexey Romanov , Rob Herring , , Kevin Hilman , , , Linus Walleij , , , , , Subject: Re: [PATCH v1 0/3] Meson A1 32-bit support Message-ID: <20230227163716.fxlczbqol2csumpa@CAB-WSD-L081021> References: <20230222115020.55867-1-avromanov@sberdevices.ru> <8e5f9bfa-d612-cd43-d722-d04c40938c62@linaro.org> <20230227142809.kujmrraf3pcdhqyn@CAB-WSD-L081021> <20230227155100.hhl4yvkyfqfyoa6h@CAB-WSD-L081021> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220415 X-Originating-IP: [172.16.1.6] X-ClientProxiedBy: S-MS-EXCH02.sberdevices.ru (172.16.1.5) To S-MS-EXCH01.sberdevices.ru (172.16.1.4) X-KSMG-Rule-ID: 4 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 1.1.2.30, bases: 2023/02/27 12:14:00 #20900843 X-KSMG-AntiVirus-Status: Clean, skipped X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230227_083720_849596_AE228B22 X-CRM114-Status: GOOD ( 23.76 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On Mon, Feb 27, 2023 at 05:15:58PM +0100, Arnd Bergmann wrote: > On Mon, Feb 27, 2023, at 16:51, Dmitry Rokosov wrote: > > On Mon, Feb 27, 2023 at 03:58:50PM +0100, Arnd Bergmann wrote: > >> > >> I would argue that is a problem with buildroot, and using a 32-bit > >> kernel is not something we should encourage over fixing buildroot > >> to do it right, or building the kernel separately from the rootfs. > >> > >> We do allow building support for a couple of ARMv8 SoCs in 32-bit > >> mode, but that is usually because they ship with a 32-bit bootrom > >> and cannot actually run a 64-bit kernel. > > > > To be honest, I didn't know about this principle. It looks like a very > > rational approach "start from max supported bitness". > > Based on overall maintainers opinion, we have to prepare a patch for > > buildroot to support compat mode :) > > That would be great, thanks a lot! > > For what it's worth, the main arguments in favor of running a 64-bit > kernel with compat user space over a 32-bit kernel are support for: > > - larger RAM sizes without highmem (most 32-bit kernels only > support 768MB of lowmem, and highmem sucks) > - larger virtual address space (4GB vs 3GB or less) > - CPU specific errata workarounds (arch/arm/ only has those for 32-bit cpus) > - mitigations for common attacks such as spectre > - security hardening that depends on larger address space > (KASLR, BTI, ptrauth, PAN, ...) > - emulating instructions that were removed in Armv8 (setend, swp, ...) > > Most of these don't apply in userspace, so the incentive to > run smaller 32-bit userland on systems with less than 1GB of > RAM usually outweighs the benefits of 64-bit userspace. Thank you very for the detailed clarification! It's strong arguments. -- Thank you, Dmitry _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic