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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 720BBC46469 for ; Wed, 12 Sep 2018 10:28:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 36DCE20866 for ; Wed, 12 Sep 2018 10:28:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 36DCE20866 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-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727756AbeILPcT (ORCPT ); Wed, 12 Sep 2018 11:32:19 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:57106 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726810AbeILPcS (ORCPT ); Wed, 12 Sep 2018 11:32:18 -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 E66BA7A9; Wed, 12 Sep 2018 03:28:24 -0700 (PDT) Received: from [10.4.12.81] (melchizedek.emea.arm.com [10.4.12.81]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 42C883F614; Wed, 12 Sep 2018 03:28:22 -0700 (PDT) Subject: Re: [PATCH v5 02/27] arm64: cpufeature: Use alternatives for VHE cpu_enable To: Julien Thierry , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, daniel.thompson@linaro.org, joel@joelfernandes.org, marc.zyngier@arm.com, mark.rutland@arm.com, christoffer.dall@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, Suzuki K Poulose References: <1535471497-38854-1-git-send-email-julien.thierry@arm.com> <1535471497-38854-3-git-send-email-julien.thierry@arm.com> From: James Morse Message-ID: <1d425320-aed3-b949-1ec5-f378248aac4d@arm.com> Date: Wed, 12 Sep 2018 11:28:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1535471497-38854-3-git-send-email-julien.thierry@arm.com> Content-Type: text/plain; charset=utf-8 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 Hi Julien, On 28/08/18 16:51, Julien Thierry wrote: > The cpu_enable callback for VHE feature requires all alternatives to have > been applied. This prevents applying VHE alternative separately from the > rest. > > Use an alternative depending on VHE feature to know whether VHE > alternatives have already been applied. > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 1e433ac..3bc1c8b 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -1022,8 +1024,15 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused) > * that, freshly-onlined CPUs will set tpidr_el2, so we don't need to > * do anything here. > */ > - if (!alternatives_applied) > - write_sysreg(read_sysreg(tpidr_el1), tpidr_el2); > + asm volatile(ALTERNATIVE( > + "mrs %0, tpidr_el1\n" > + "msr tpidr_el2, %0", > + "nop\n" > + "nop", > + ARM64_HAS_VIRT_HOST_EXTN) > + : "+r" (tmp) > + : > + : "memory"); > } > #endif Catalin's preference was to keep this all in C: https://patchwork.kernel.org/patch/10007977/ , for which we need to know if 'the' alternative has been applied. I suspect there may be more registers in this list if we have to switch to another EL2 register using alternatives. (but I don't have an example). Could we make 'alternatives_applied' a macro that takes the cap as an argument? Thanks, James