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 48418C388F2 for ; Thu, 22 Oct 2020 13:49:32 +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 CDEE121D43 for ; Thu, 22 Oct 2020 13:49:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="BLW7KYVi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CDEE121D43 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=9NySwCdD169WcsaoD4vX2VWZ9sjvFbvdfWNcx2btcxI=; b=BLW7KYViA6I6p1rMsceJC1dz2 pPcENCfpj9ITTlYpZuUV6d37VNoAYJimv0voXYQlXMYivccUCnLQyfqxSYKbB+YIlh8r5gLcXVeTI ubkE1HkbQFRf4WN8ILf2UFamPnNZ0W6PCJmcyjYoVA78uEXqafgTBbQTDSu6XHwyKglvpFyRb6pgZ FqoQ0wlghzL5TmADBmYG4TE9qjDe1mp+Hrq7mfwQRt3bJtrgihG60xxlvmzY4V59+Whg6MzpCv97V I3bglBPnbDP+I1J2LRgHI86RnzE0sfAJRmf3mdxbRb4S2vcUJt5G7QuOKhLSe9u2cH6A+PlN26/fP LXDPav57A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVawk-0004VA-5v; Thu, 22 Oct 2020 13:48:02 +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 1kVawh-0004UU-Ep for linux-arm-kernel@lists.infradead.org; Thu, 22 Oct 2020 13:48:00 +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 E073E101E; Thu, 22 Oct 2020 06:47:55 -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 8C9993F66E; Thu, 22 Oct 2020 06:47:54 -0700 (PDT) Date: Thu, 22 Oct 2020 14:47:52 +0100 From: Qais Yousef To: Will Deacon Subject: Re: [RFC PATCH v2 4/4] arm64: Export id_aar64fpr0 via sysfs Message-ID: <20201022134752.wtcdkbi4fjn2blh6@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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201021144112.GA17912@willie-the-truck> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201022_094759_564912_27514EFB X-CRM114-Status: GOOD ( 18.90 ) 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 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 ? I just need to make sure that Peter and Greg are happy with this arm64 specific mask added to sysfs in this manner. Not sure if there's a precedent of archs exporting special masks in sysfs. Or maybe people had something else in mind about how his this mask should be exported? Thanks -- Qais Yousef _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel