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=-6.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 BB13CC4338F for ; Sun, 15 Aug 2021 07:28:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9308160E52 for ; Sun, 15 Aug 2021 07:28:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236433AbhHOH3Y (ORCPT ); Sun, 15 Aug 2021 03:29:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46340 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236146AbhHOH3X (ORCPT ); Sun, 15 Aug 2021 03:29:23 -0400 Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EABB6C061764 for ; Sun, 15 Aug 2021 00:28:53 -0700 (PDT) Received: by mail-pj1-x102c.google.com with SMTP id mq2-20020a17090b3802b0290178911d298bso22457735pjb.1 for ; Sun, 15 Aug 2021 00:28:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=cn/+Frc54mS+Ha2Lobee22sCIkMscZ5re9djGEP3QzE=; b=HdF3gao57FQhc4op+Z08XKW7iXonIW2f6C3zevEzMN2PvVcasXubg4GMGjhXCJpQMB omJGL2L6u+Zt3mySJUtN+bP79cYystJ/tRH6r7xfuPVduVkdUUO0/2EupWHZrUg2tqBv s8pVdNsqqzzi2Dokaxn/3/k9fqNBU7zo0hElBpOHGQsO7h2bOwTFDJKdpz2/NUe+N6Eu nb1Gt6hMcWW7iM94QlnNYV95IdoSepr7T11KXJB3uGlLUyVbY2jelQtl/bjtpKUyymYS whxEHhv6+OTsPwilpIV+jLDK7hj6aq+4DoSEzRuQhdnbIUlHjdI2gyH1Dh5SDgQ/Cd4h FXDw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=cn/+Frc54mS+Ha2Lobee22sCIkMscZ5re9djGEP3QzE=; b=svLsxHk05ONJrCIZfEfh9uN49T25/s8oIp5md2xVjzPVVkA7tl8qz7cnVAfg4JNruo J+70C/CqQG7p6T4K8FjcW2Z8lGBILiG1mitgjuQ+jUsGlZehU7DuENccRy6HECJ2uqlj owOsp83M7aj2uk77T1+QyF6xcFkm9wmv5Zfm4X0aPfKtCv16RjKqhPtYxJQrs0VB/Qrd 905czHnuwJshyAf/oI6mPgY4+knw1NSgwYU+xJH7t4SjlcJ2JqnNoIQXXoTIIOCaFzIy oD86yjA0FvIYRXTnwQasgN3uDZ5a2uljr10ap+SIOvJLa5q+TwHKxQmxuu/cjO72uIvg 8Ppg== X-Gm-Message-State: AOAM530+LOWaEdGATUUjb7weSzrCVjx9QQeR+OoLk+lPCYBsu0QpRpM/ 9QD+mrc1WM/Y6YylVkkmXBY= X-Google-Smtp-Source: ABdhPJwrWmWWu+2lk+8Z95VUhJyjjEWzMM/tLQbMaiOwf/18RoS/YvsL7l9/7O3QkubasGwB6fM+kg== X-Received: by 2002:a65:62d1:: with SMTP id m17mr10192429pgv.370.1629012533446; Sun, 15 Aug 2021 00:28:53 -0700 (PDT) Received: from [10.230.32.65] ([192.19.148.250]) by smtp.gmail.com with ESMTPSA id b17sm8375667pgl.61.2021.08.15.00.28.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 15 Aug 2021 00:28:52 -0700 (PDT) Subject: Re: [PATCH 0/5] arm64: Survival kit for SCR_EL3.HCE==0 conditions To: Marc Zyngier , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Will Deacon , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com References: <20210812190213.2601506-1-maz@kernel.org> From: Florian Fainelli Message-ID: <7ffa35bb-1f2c-19ff-fe4b-33267fba80e8@gmail.com> Date: Sun, 15 Aug 2021 09:28:47 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210812190213.2601506-1-maz@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/12/2021 9:02 PM, Marc Zyngier wrote: > Anyone vaguely familiar with the ARMv8 architecture would quickly > understand that entering the kernel at EL2 without enabling the HVC > instruction is... living dangerously. But as it turns out [0], there > is a whole range of (*cough*) "high quality" (*cough*) Broadcom > systems out there configured exactly like that. Some Broadcom systems, namely the 4908 and all of those using CFE, they later switched to u-boot and ATF and got it right. > > If you are speechless, I'm right with you. > > These machines have stopped being able to boot an upstream kernel > since 5.12, where we changed the way we switch from nVHE to VHE, as > this relies on the HVC instruction being usable... It is also worth > noting that these systems have never been able to use KVM. Or kexec. > > This small series addresses the issue by detecting an UNDEFing HVC in > a fairly controlled environment, and in this case pretend that we have > booted at EL1. It also documents the requirement for SCR_EL3.HCE to be > set to *1* if the kernel is entered at EL2. Turns out that we really > have to state the obvious. > > This has been tested on a FVP model with a hacked-up boot-wrapper. > > Note that I really don't think any of this is -stable material, except > maybe for the documentation. It isn't 5.14 material either. Best case, > this is 5.15, or maybe even later. If ever. While I am very appreciative of the work you have done here to try to get the dysfunctional systems to warn and continue to boot, I would rather we try to load a minimal shim at EL3 capable of fixing up any incorrect EL3 register setting ahead of loading the kernel provided this is possible at all on a commercially available system. Rafal, is this something that CFE allows you to do (as I could not get a straight answer from that team), if so have you tried it? -- Florian