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=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 527EEC4338F for ; Sun, 22 Aug 2021 11:31:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2688D610E6 for ; Sun, 22 Aug 2021 11:31:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233376AbhHVLcc (ORCPT ); Sun, 22 Aug 2021 07:32:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232822AbhHVLcb (ORCPT ); Sun, 22 Aug 2021 07:32:31 -0400 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE683C061575 for ; Sun, 22 Aug 2021 04:31:50 -0700 (PDT) Received: by mail-pl1-x62c.google.com with SMTP id n12so8535317plf.4 for ; Sun, 22 Aug 2021 04:31:50 -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=uG8L86QsABhqIwwrydn4T4dyHIpTrRxaUr9DrrinnwM=; b=l7SzrK0oaNhCcHt3E8VCYzXFX6OdelfMnmQ4dHsFQ8jR1Gr78k59aO7yKKJRxl2Smq NnvsA0bNbiMcKTvGJ69azmWt3OA0b273iXiFG8snU2bnbJE1lAlMh0H7CDKOwrDr3v4F DTmg9B6q8D3XYY10kROF747L3MfsOySEgi8+30LnWak1TNLUHBAUm2Lvh0ELe/1REo4q +VKXo8k/QJItqI8pojbff+ebfpcFzpT99fjNvwxtdJOx5ybBqSuyafl6i8ybClNdYsEt ekXhdNS9lHS7ZtXQd3TjwGL/Oc4WUwRHItt0HlPwbbChHED6JTWmu82wZIUd1F5ICkQ8 7Gng== 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=uG8L86QsABhqIwwrydn4T4dyHIpTrRxaUr9DrrinnwM=; b=O2AEjAYtFUDDGsBQnxGopsKMYaAoSZnbjkk476Ymtgq1J+Uwkb9IAyL3o2i9KQ+UHh 501KSlijbeSDUXE07m3PXIyc+YVLrrAZ058Sh3Hz2SFJuBla3u5ljUh4D5c0mpqAYflB 2RMiqXJrtDVGj+FQTN+HPsp8BiIFbtJMo4xOmqXzxeMjGCMjlA2osQdC1SvZJYpbLTeO 3lOo8gLvbdhYpvIGdhhRCW7SCgLUjkiiQc5HfORQbAhXWQUT0twOv9DkP/69UpxHCE3E AEX8ebYRZhcwyA3iPbMxg8jdpOr0suulSpdGhlr7RZJ0W4RKKjjUUUHb6SRBT5puf9VE n4iA== X-Gm-Message-State: AOAM530CR5yc91yCCApeQZq17qUS2tBEThOl5bUqPItwWpZ0mi50JrVr gLy9HteP0Nb36aoH4nauVHo= X-Google-Smtp-Source: ABdhPJw6tKO7hQ6MCmq1ZROVlWfDeX1cTvVIteWiV9X19pBYrc5vUsBuw+myU5VcWIPvSDU/x7/IMQ== X-Received: by 2002:a17:90a:c481:: with SMTP id j1mr14469626pjt.164.1629631910175; Sun, 22 Aug 2021 04:31:50 -0700 (PDT) Received: from [10.230.31.46] ([192.19.223.252]) by smtp.gmail.com with ESMTPSA id z2sm15074459pgb.33.2021.08.22.04.31.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Aug 2021 04:31:49 -0700 (PDT) Subject: Re: [PATCH 0/5] arm64: Survival kit for SCR_EL3.HCE==0 conditions To: Marc Zyngier , Florian Fainelli Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , Will Deacon , Catalin Marinas , Mark Rutland , Ard Biesheuvel , bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com References: <20210812190213.2601506-1-maz@kernel.org> <7ffa35bb-1f2c-19ff-fe4b-33267fba80e8@gmail.com> <874kbr12in.wl-maz@kernel.org> From: Florian Fainelli Message-ID: <0d3de5dd-f85c-d6d6-2c1b-1248847c0a09@gmail.com> Date: Sun, 22 Aug 2021 13:31:38 +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: <874kbr12in.wl-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 8/15/2021 11:27 AM, Marc Zyngier wrote: > On Sun, 15 Aug 2021 08:28:47 +0100, > Florian Fainelli wrote: >> >> >> >> 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. > > Do we have a list of the affected systems? That is going to be hard to come up with given that OEMs such as Asus, TP-Link, or Netgear and multiple devices are affected. I would start with this list which is far from exhaustive: Netgear R8000P, TP-Link Archer C2300, Asus GT AC5300. > >> >>> >>> 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. > > That would be the best thing to do, and would make the machine fully > usable. I still think we need to have something in the kernel to at > least let the user know that their system is misconfigured though. > > If CFE allows a payload to be loaded at EL3 and executed on all CPUs, > that would be absolutely awesome. It would even allow switching over > to ATF... Supposedly there are GPL tarballs containing an u-boot that is suitable for the 4908, however I have no idea where to find those. In premise you could chainload those to CFE and a get seemingly functional system. -- Florian