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 ACFCDC282DD for ; Fri, 10 Jan 2020 18:41:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7F1492082E for ; Fri, 10 Jan 2020 18:41:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728668AbgAJSlw (ORCPT ); Fri, 10 Jan 2020 13:41:52 -0500 Received: from foss.arm.com ([217.140.110.172]:49904 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728083AbgAJSlw (ORCPT ); Fri, 10 Jan 2020 13:41:52 -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 D11E830E; Fri, 10 Jan 2020 10:41:51 -0800 (PST) Received: from [10.1.197.1] (ewhatever.cambridge.arm.com [10.1.197.1]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9A8B03F6C4; Fri, 10 Jan 2020 10:41:50 -0800 (PST) Subject: Re: [PATCH v2 2/7] arm64: fpsimd: Make sure SVE setup is complete before SIMD is used To: Catalin Marinas 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 References: <20191217183402.2259904-1-suzuki.poulose@arm.com> <20191217183402.2259904-3-suzuki.poulose@arm.com> <20200110115132.GA8786@arrakis.emea.arm.com> From: Suzuki Kuruppassery Poulose Message-ID: Date: Fri, 10 Jan 2020 18:41:49 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: <20200110115132.GA8786@arrakis.emea.arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/01/2020 11:51, Catalin Marinas wrote: > 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). Thanks for pointing out. I missed this from the Dave's last email. I have added a WARN_ON(!system_capabilities_finalized()) to may_use_simd() for the next version. Thanks for the review ! Suzuki