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 845AEC64ED8 for ; Mon, 27 Feb 2023 16:51:11 +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=7wTEzwXTlFnh3CDCjvYVvhBWlFdkn3B0JrCouxI/vA0=; b=vt4Sjf/PG+jQIe 3Rp6Z4Adgs+E8uJzJMrtsO8GTcz5EzDpGd/FF32osNVLLbL6HjPt89X77POf2mU9tkdaYGUbnywEU q6G0GyoOn6tO0+Vgz1+JoScpjYdbHt9IkXdpXQtnlXr+CeP1YpqSToETrPkV/0Cd/tmmqMhHTabcE eBbuTqYJJ161rzb3XLg2tImZtzMnJjhpMM101kabVJBH/CFtLr1xPKePE/K9+S4iYVVahKofatZRP 8/qwO19mFM4r+1upAvhwVYIbZWOQTrLE2b/IKDgTwq8oNB/Jb7stsJbepgxMv/B8oawkgBerzjrNI tkbw7D2ILyOozalryzDA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pWgiH-00APFb-6e; Mon, 27 Feb 2023 16:50:57 +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 1pWgiD-00APEv-IA; Mon, 27 Feb 2023 16:50:55 +0000 Received: from s-lin-edge02.sberdevices.ru (localhost [127.0.0.1]) by mx.sberdevices.ru (Postfix) with ESMTP id 411865FD23; Mon, 27 Feb 2023 19:50:50 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sberdevices.ru; s=mail; t=1677516650; bh=+o4MePp9OqmjWmI8f3GoSonJgPXKEx/DY7E2POpmxqc=; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type; b=Is6lD68TXQ+LXSIPeMLcaY1cQuni31x7+SQTRswGrgqyp1Mf2TQmsF19mebjjkdlE SStVzS24WRa1eM3iw3/Zlbs/gA0Av69UL/+Oj/1+v4sNSW9I1IpMOafYnZhS1a5NBB GpBK27em27UMsN/Sv9qNT/guVqMviPD3K3nB4pfcU3sP0T3NjDGgPkkiptdbWsNIa+ fTcQiGRGseNijIEhHc6k6IQYbzRdG5aT3ud/9nnGYtbx829b/9JD4Yhqb4TYsm2ktu 5mBosKSROlE1B3fb3F/J3g+cL8hvlJYP+wNsIoyXXgDiMhMOSX/tQnIchiIjysI0LW mnnZsZ5PoetSQ== 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 19:50:49 +0300 (MSK) Date: Mon, 27 Feb 2023 19:50:49 +0300 From: Dmitry Rokosov To: Neil Armstrong CC: Arnd Bergmann , Alexey Romanov , Rob Herring , , Kevin Hilman , , , Linus Walleij , , , , , Subject: Re: [PATCH v1 0/3] Meson A1 32-bit support Message-ID: <20230227165049.4y7jx5nnnlibe6kg@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> <33b58877-5167-c453-e686-1d10cdca66c0@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <33b58877-5167-c453-e686-1d10cdca66c0@linaro.org> User-Agent: NeoMutt/20220415 X-Originating-IP: [172.16.1.6] X-ClientProxiedBy: S-MS-EXCH01.sberdevices.ru (172.16.1.4) 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_085054_028833_A487C5A6 X-CRM114-Status: GOOD ( 27.02 ) 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 05:38:49PM +0100, Neil Armstrong wrote: > On 27/02/2023 17:15, 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. > > Thanks for the details! Looks like Thomas has already prepared a basic patch series for buildroot, but maintainers declined it. https://lore.kernel.org/all/20220730194331.GA2515056@scaer/ -- Thank you, Dmitry _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic