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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 E4775C04AB5 for ; Mon, 3 Jun 2019 16:25:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C434824592 for ; Mon, 3 Jun 2019 16:25:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729080AbfFCQZj (ORCPT ); Mon, 3 Jun 2019 12:25:39 -0400 Received: from foss.arm.com ([217.140.101.70]:55106 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726720AbfFCQZj (ORCPT ); Mon, 3 Jun 2019 12:25:39 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 54CBA80D; Mon, 3 Jun 2019 09:25:39 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3D64E3F5AF; Mon, 3 Jun 2019 09:25:37 -0700 (PDT) Date: Mon, 3 Jun 2019 17:25:34 +0100 From: Catalin Marinas To: Julien Grall Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, will.deacon@arm.com, christoffer.dall@arm.com, marc.zyngier@arm.com, james.morse@arm.com, julien.thierry@arm.com, suzuki.poulose@arm.com, Dave.Martin@arm.com, ard.biesheuvel@linaro.org Subject: Re: [PATCH v5 3/3] arm64/fpsimd: Don't disable softirq when touching FPSIMD/SVE state Message-ID: <20190603162534.GF63283@arrakis.emea.arm.com> References: <20190521172139.21277-1-julien.grall@arm.com> <20190521172139.21277-4-julien.grall@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190521172139.21277-4-julien.grall@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, May 21, 2019 at 06:21:39PM +0100, Julien Grall wrote: > Since a softirq is supposed to check may_use_simd() anyway before > attempting to use FPSIMD/SVE, there is limited reason to keep softirq > disabled when touching the FPSIMD/SVE context. Instead, we can simply > disable preemption and mark the FPSIMD/SVE context as in use by setting > CPU's fpsimd_context_busy flag. [...] > +static void get_cpu_fpsimd_context(void) > +{ > + preempt_disable(); > + __get_cpu_fpsimd_context(); > +} Is there anything that prevents a softirq being invoked between preempt_disable() and __get_cpu_fpsimd_context()? -- Catalin