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=-3.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 12C37C388F9 for ; Thu, 22 Oct 2020 14:35:48 +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 875D924171 for ; Thu, 22 Oct 2020 14:35:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="gHti8gxV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 875D924171 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com 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=8Y+E8VLsTb/tD8qdzsgoYgA3SA7laZ+UBjK92q7/O4U=; b=gHti8gxVtBV56NTUdN8yyEZ03 rLuO9tI1DAt5aufnb8yl+u+be2NJvi4siwpjp3kqOavj0gPGjci5TGWCNnFthMxemrJrXHUEgkNGU 5d/aeUkb/sQGgaSfhUaRZTX0IYpK/vDs8/g/FL/pK8/c2Bxl1ITgT9dgluUqPq8WuHxd2rgnLsmpC Zd82Msui0AfBRM2kG+H5Jb5T0HMe5WnrAh69YSlIONEgJR9d8DYgmhcolVn4+vMspiqhMAwOR3MzS x6CYsrRIYxwkVpXMfZgh/4xXmoPX7LEQke4YwtRAfkr8BvOGlEL+Jm9dWRbZBvWLQ9vW7WzAISnkr 8M30tKV8Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVbfh-0000kM-7q; Thu, 22 Oct 2020 14:34:29 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVbfd-0000jF-AH for linux-arm-kernel@lists.infradead.org; Thu, 22 Oct 2020 14:34:26 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6D276D6E; Thu, 22 Oct 2020 07:34:22 -0700 (PDT) Received: from e107158-lin (e107158-lin.cambridge.arm.com [10.1.194.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1CA383F66E; Thu, 22 Oct 2020 07:34:21 -0700 (PDT) Date: Thu, 22 Oct 2020 15:34:18 +0100 From: Qais Yousef To: Catalin Marinas Subject: Re: [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs Message-ID: <20201022143418.utd6vfl7ii3essal@e107158-lin> 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> <20201022134752.wtcdkbi4fjn2blh6@e107158-lin> <20201022135559.GB1788090@kroah.com> <20201022143102.GH1229@gaia> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201022143102.GH1229@gaia> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201022_103425_431294_22E24407 X-CRM114-Status: GOOD ( 27.83 ) 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, Will Deacon , "Peter Zijlstra \(Intel\)" , Greg Kroah-Hartman , James Morse , Marc Zyngier , 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 10/22/20 15:31, Catalin Marinas wrote: > On Thu, Oct 22, 2020 at 03:55:59PM +0200, Greg Kroah-Hartman wrote: > > On Thu, Oct 22, 2020 at 02:47:52PM +0100, Qais Yousef wrote: > > > On 10/21/20 15:41, Will Deacon wrote: > > > > > We already expose MIDR and REVIDR via the current sysfs interface. We > > > > > can expand it to include _all_ the other ID_* regs currently available > > > > > to user via the MRS emulation and we won't have to debate what a new > > > > > interface would look like. The MRS emulation and the sysfs info should > > > > > probably match, though that means we need to expose the > > > > > ID_AA64PFR0_EL1.EL0 field which we currently don't. > > > > > > > > > > I do agree that an AArch32 cpumask is an easier option both from the > > > > > kernel implementation perspective and from the application usability > > > > > one, though not as easy as automatic task placement by the scheduler (my > > > > > first preference, followed by the id_* regs and the aarch32 mask, though > > > > > not a strong preference for any). > > > > > > > > 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. > > > > > > So the mask idea is about adding a new > > > > > > /sys/devices/system/cpu/aarch32_cpus > > > > > > ? > > > > Is this a file, a directory, or what? What's the contents? > > > > Without any of that, I have no idea if it's "ok" or not... > > I don't know what Qais thinks but a file matching the syntax of the > present/online/offline/possible files (e.g. 0-3) would look more > consistent. Yes. Sorry I thought it's obvious. Thanks -- Qais Yousef _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel