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 X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CFF2DC388F9 for ; Wed, 21 Oct 2020 17:25:31 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 552752224E for ; Wed, 21 Oct 2020 17:25:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="N1WO+1QA"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="j+ncN65M" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 552752224E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject: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=mTpAUf+RpLtRbGDUYBoKMXFlGJw3zwGyRLazdd8vTFA=; b=N1WO+1QATWh64CsKVMYfHx6Zu /yB3GNvT/w4uXn8kpFT2RKGT/d8s99AqO1/JtwTRvu6/vt5q4RtbQa5o4gkVapZlx9uh+QbCk7O6C DGjLwxtvpd2AlgubenILmVgXMd6r+4EjU0ho5chaK0qQ7JNcCjYVAzJitt+m8JbTHcJWso5IUpIOt 0mEEGFqjZxpL/Z2OjK9Qw8wcf1HjSbl2hTKyF8slVZ+vRnTT9beoHfLaC6BPt+MKhB5mhSDxRkjux WL+L0afbTka1J0UWKP3+kHt1s54CALrXy/B3pVUEFxFdnf2AoyLAqhyHLS9zO/jXyjAkeAqrdqlUL T46nStfTA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVHq7-0003em-N7; Wed, 21 Oct 2020 17:23:55 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVHq4-0003dv-U5 for linux-arm-kernel@lists.infradead.org; Wed, 21 Oct 2020 17:23:53 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 990332224E; Wed, 21 Oct 2020 17:23:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603301031; bh=xq9F3BNwrdzcMaeiCuh+tv2UemTAqtVTeWOtyKnQsxM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=j+ncN65MDIe17KRnakxuyrEDqKSURzcGQnDCDtguNYVz5cMwquYGFvIsC9X1JESTi LIUDla4jGek6RZFQOW2xN+Am7dTAnKEtji9WiqXtqm/sdV9WYRg8eGetOQXovF36VS 1TI7oAb6XM+8lIKEuFc6ItikkaH/wNzlJgO8YoPs= Date: Wed, 21 Oct 2020 18:23:46 +0100 From: Will Deacon To: Qais Yousef Subject: Re: [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs Message-ID: <20201021172345.GF18071@willie-the-truck> References: <20201021104611.2744565-1-qais.yousef@arm.com> <20201021104611.2744565-5-qais.yousef@arm.com> <63fead90e91e08a1b173792b06995765@kernel.org> <20201021121559.GB3976@gaia> <20201021144112.GA17912@willie-the-truck> <20201021150313.ecxawwxsowweye43@e107158-lin> <20201021152310.GA18071@willie-the-truck> <20201021160730.komcgrp7q2tly55w@e107158-lin> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201021160730.komcgrp7q2tly55w@e107158-lin> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201021_132353_083757_9C7A1949 X-CRM114-Status: GOOD ( 28.39 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Marc Zyngier , "Peter Zijlstra \(Intel\)" , Catalin Marinas , James Morse , Greg Kroah-Hartman , Linus Torvalds , Morten Rasmussen , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Oct 21, 2020 at 05:07:30PM +0100, Qais Yousef wrote: > On 10/21/20 16:23, Will Deacon wrote: > > > > If a cpumask is easier to implement and easier to use, then I think that's > > > > what we should do. It's also then dead easy to disable if necessary by > > > > just returning 0. The only alternative I would prefer is not having to > > > > expose this information altogether, but I'm not sure that figuring this > > > > out from MIDR/REVIDR alone is reliable. > > > > > > I did suggest this before, but I'll try gain. If we want to assume a custom > > > bootloader and custom user space, we can make them provide the mask. > > > > Who mentioned a custom bootloader? In the context of Android, we're > > Custom bootloader as in a bootloader that needs to opt-in to enable the > feature (pass the right cmdline param). Catalin suggested to make this a sysctl > to allow also for runtime toggling. But the initial intention was to have this > to enable it at cmdline. Hmm, ok, I don't think allowing the cmdline to be specified means its a custom bootloader. > > talking about a user-space that already manages scheduling affinity. > > > > > For example, the new sysctl_enable_asym_32bit could be a cpumask instead of > > > a bool as it currently is. Or we can make it a cmdline parameter too. > > > In both cases some admin (bootloader or init process) has to ensure to fill it > > > correctly for the target platform. The bootloader should be able to read the > > > registers to figure out the mask. So more weight to make it a cmdline param. > > > > I think this is adding complexity for the sake of it. I'm much more in > > I actually think it reduces complexity. No special ABI to generate the mask > from the kernel. The same opt-in flag is the cpumask too. Maybe I'm misunderstanding your proposal but having a cpumask instead of a bool means you now have to consider policy on a per-cpu basis, which adds an extra dimension to this. For example, do you allow that mask to be changed at runtime so that differents sets of CPUs now support 32-bit? Do you preserve it across hotplug? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel