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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 33BB0C33CA2 for ; Fri, 10 Jan 2020 11:51:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14B472072A for ; Fri, 10 Jan 2020 11:51:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727919AbgAJLvh (ORCPT ); Fri, 10 Jan 2020 06:51:37 -0500 Received: from foss.arm.com ([217.140.110.172]:42992 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727689AbgAJLvg (ORCPT ); Fri, 10 Jan 2020 06:51:36 -0500 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 5F0301063; Fri, 10 Jan 2020 03:51:36 -0800 (PST) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.197.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0F4573F534; Fri, 10 Jan 2020 03:51:34 -0800 (PST) Date: Fri, 10 Jan 2020 11:51:32 +0000 From: Catalin Marinas To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, will@kernel.org, maz@kernel.org, mark.rutland@arm.com, dave.martin@arm.com, ard.biesheuvel@linaro.org, christoffer.dall@arm.com, Will Deacon Subject: Re: [PATCH v2 2/7] arm64: fpsimd: Make sure SVE setup is complete before SIMD is used Message-ID: <20200110115132.GA8786@arrakis.emea.arm.com> References: <20191217183402.2259904-1-suzuki.poulose@arm.com> <20191217183402.2259904-3-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191217183402.2259904-3-suzuki.poulose@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 17, 2019 at 06:33:57PM +0000, Suzuki K Poulose wrote: > In-kernel users of NEON rely on may_use_simd() to check if the SIMD > can be used. However, we must initialize the SVE before SIMD can > be used. Add a sanity check to make sure that we have completed the > SVE setup before anyone uses the SIMD. > > Cc: Ard Biesheuvel > Cc: Mark Rutland > Cc: Will Deacon > Cc: Catalin Marinas > Signed-off-by: Suzuki K Poulose > --- > Discussion here : https://lkml.kernel.org/r/20191014145204.GS27757@arm.com Re-reading this thread, I think the conclusion was more towards having a WARN_ON in system_supports_fpsimd() (or may_use_simd()). We don't expect code to start using neon before the SMP is initialised (other than early_initcall(), the rest run after the secondary CPUs are brought up). -- Catalin