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 90412C282DD for ; Fri, 10 Jan 2020 14:50:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B2322080D for ; Fri, 10 Jan 2020 14:50:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728328AbgAJOuY (ORCPT ); Fri, 10 Jan 2020 09:50:24 -0500 Received: from foss.arm.com ([217.140.110.172]:45656 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727627AbgAJOuX (ORCPT ); Fri, 10 Jan 2020 09:50:23 -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 383B6328; Fri, 10 Jan 2020 06:50:23 -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 DE2443F6C4; Fri, 10 Jan 2020 06:50:21 -0800 (PST) Date: Fri, 10 Jan 2020 14:50:19 +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 1/7] arm64: Introduce system_capabilities_finalized() marker Message-ID: <20200110145019.GD8786@arrakis.emea.arm.com> References: <20191217183402.2259904-1-suzuki.poulose@arm.com> <20191217183402.2259904-2-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191217183402.2259904-2-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 06:33:56PM +0000, Suzuki K Poulose wrote: > We finalize the system wide capabilities after the SMP CPUs > are booted by the kernel. This is used as a marker for deciding > various checks in the kernel. e.g, sanity check the hotplugged > CPUs for missing mandatory features. > > However there is no explicit helper available for this in the > kernel. There is sys_caps_initialised, which is not exposed. > The other closest one we have is the jump_label arm64_const_caps_ready > which denotes that the capabilities are set and the capability checks > could use the individual jump_labels for fast path. This is > performed before setting the ELF Hwcaps, which must be checked > against the new CPUs. We also perform some of the other initialization > e.g, SVE setup, which is important for the use of FP/SIMD > where SVE is supported. Normally userspace doesn't get to run > before we finish this. However the in-kernel users may > potentially start using the neon mode. So, we need to > reject uses of neon mode before we are set. Instead of defining > a new marker for the completion of SVE setup, we could simply > reuse the arm64_const_caps_ready and enable it once we have > finished all the setup. Also we could expose this to the > various users as "system_capabilities_finalized()" to make > it more meaningful than "const_caps_ready". > > Cc: Ard Biesheuvel > Cc: Will Deacon > Cc: Catalin Marinas > Cc: Mark Rutland > Signed-off-by: Suzuki K Poulose Reviewed-by: Catalin Marinas