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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,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 5161AC10F14 for ; Tue, 15 Oct 2019 14:05:56 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id EC0FB207FF for ; Tue, 15 Oct 2019 14:05:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="t9EpwFxO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC0FB207FF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.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=ao6HD9Hmga9I9NrASmoaWFQ5xA5I9r9cwSMUNbfVd3w=; b=t9EpwFxOKLAnxI 0f4ZNEMWHmGzTOpR61HBleACePJUxq6xW8nFqrByFxt1kBbI5p6YCf9rTET3+npGatZdmwInDlaEE LsviZzGgS39/GpgGz+gYxVlSNavcfmYJUNKEbJLyPHQh/+OHcdmTS/NNobx/zD1Apx2YjdJDUfklH KOI4vThDlC2FppjUxkSdVburA9q5HY/J92ff8CpAqCXoCHeVOH8D9VbLvLq6Gbtv43FFT3wiNiH7v eiyhb42mubGJF2AJiDqMYojd/7A5ZcuPuR2LW8ZKMyVQaZLKtXFexlo5H6z4c44zHFgjE+NVJcaVk /WQ8dbjbJ31P7ZlzbYag==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iKNSP-0007Ng-UY; Tue, 15 Oct 2019 14:05:49 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iKNSM-0007MN-GW for linux-arm-kernel@lists.infradead.org; Tue, 15 Oct 2019 14:05:47 +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 25D30337; Tue, 15 Oct 2019 07:05:45 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 237813F718; Tue, 15 Oct 2019 07:05:44 -0700 (PDT) Date: Tue, 15 Oct 2019 15:05:42 +0100 From: Dave Martin To: Ard Biesheuvel Subject: Re: [PATCH 1/3] arm64: cpufeature: Fix the type of no FP/SIMD capability Message-ID: <20191015140541.GW27757@arm.com> References: <20191011113620.GG27757@arm.com> <4ba5c423-4e2a-d810-cd36-32a16ad42c91@arm.com> <20191011142137.GH27757@arm.com> <418b0c4b-cbcd-4263-276d-1e9edc5eee0b@arm.com> <20191014145204.GS27757@arm.com> <12e002e7-42e8-c205-e42c-3348359d2f98@arm.com> <20191014155009.GM24047@e103592.cambridge.arm.com> <20191015102459.GV27757@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191015_070546_590965_1AEC07DA X-CRM114-Status: GOOD ( 15.27 ) 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: Mark Rutland , Suzuki Poulose , Catalin Marinas , "linux-kernel@vger.kernel.org" , "will@kernel.org" , "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+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Oct 15, 2019 at 12:30:15PM +0200, Ard Biesheuvel wrote: > On Tue, 15 Oct 2019 at 12:25, Dave Martin wrote: > > > > On Mon, Oct 14, 2019 at 06:57:30PM +0200, Ard Biesheuvel wrote: [...] > > > All in-kernel NEON code checks whether the NEON is usable, so I'd > > > expect that check to return 'false' if it is too early in the boot for > > > the NEON to be used at all. > > > > My concern is that the check may be done once, at probe time, for crypto > > drivers. If probing happens before system_supports_fpsimd() has > > stabilised, we may be stuck with the wrong probe decision. > > > > So: are crypto drivers and kernel_mode_neon() users definitely only > > probed _after_ all early CPUs are up? > > > > Isn't SMP already up when initcalls are processed? That was my original assumption when developing SVE. I think I convinced myself that it was valid, but it sounds worth reinvestigating. Assuming the assumption _is_ valid, then dropping a suitable WARN() into system_supports_fpsimd() or cpu_has_neon() or similar may be a good idea. Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel