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=-12.0 required=3.0 tests=BAYES_00,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 3D156C4338F for ; Thu, 12 Aug 2021 19:02:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D7AC610A3 for ; Thu, 12 Aug 2021 19:02:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235197AbhHLTDF (ORCPT ); Thu, 12 Aug 2021 15:03:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:59260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234302AbhHLTC7 (ORCPT ); Thu, 12 Aug 2021 15:02:59 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E862A6108C; Thu, 12 Aug 2021 19:02:33 +0000 (UTC) Received: from sofa.misterjones.org ([185.219.108.64] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1mEFyJ-004c9r-W0; Thu, 12 Aug 2021 20:02:32 +0100 From: Marc Zyngier To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= , Will Deacon , Catalin Marinas , Mark Rutland , Ard Biesheuvel , Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com Subject: [PATCH 0/5] arm64: Survival kit for SCR_EL3.HCE==0 conditions Date: Thu, 12 Aug 2021 20:02:08 +0100 Message-Id: <20210812190213.2601506-1-maz@kernel.org> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, zajec5@gmail.com, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, ardb@kernel.org, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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. M. (drink required) [0] https://lore.kernel.org/r/53f3a2d2-22f8-edee-2507-d41a4090dad7@gmail.com Marc Zyngier (5): arm64: Directly expand __init_el2_nvhe_prepare_eret where needed arm64: Handle UNDEF in the EL2 stub vectors arm64: Detect disabled HVC early arm64: Warn on booting at EL2 with HVC disabled arm64: Document the requirement for SCR_EL3.HCE Documentation/arm64/booting.rst | 5 +++++ arch/arm64/include/asm/el2_setup.h | 6 ------ arch/arm64/include/asm/virt.h | 10 +++++++++ arch/arm64/kernel/head.S | 34 ++++++++++++++++++++++++++++++ arch/arm64/kernel/hyp-stub.S | 19 ++++++++++++++++- arch/arm64/kernel/smp.c | 3 +++ 6 files changed, 70 insertions(+), 7 deletions(-) -- 2.30.2