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,URIBL_BLOCKED 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 D829EC433F5 for ; Fri, 31 Aug 2018 13:20:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 964082083A for ; Fri, 31 Aug 2018 13:20:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 964082083A 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 S1727946AbeHaR2V (ORCPT ); Fri, 31 Aug 2018 13:28:21 -0400 Received: from foss.arm.com ([217.140.101.70]:57996 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727265AbeHaR2V (ORCPT ); Fri, 31 Aug 2018 13:28:21 -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 8304E7A9; Fri, 31 Aug 2018 06:20:53 -0700 (PDT) Received: from [10.4.13.35] (ostrya.emea.arm.com [10.4.13.35]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BCABD3F5BC; Fri, 31 Aug 2018 06:20:50 -0700 (PDT) Subject: Re: [RFC 09/13] iommu/smmuv3: Get prepared for nested stage support To: Eric Auger , "\"eric.auger.pro"@gmail.com, eric.auger@redhat.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, joro@8bytes.org, alex.williamson@redhat.com, jean-philippe.brucker@arm.com, jacob.jun.pan@linux.intel.com, "yi.l.liu\""@linux.intel.com, will.deacon@arm.com, robin.murphy@arm.com Cc: marc.zyngier@arm.com, peter.maydell@linaro.org, christoffer.dall@arm.com References: <1535026656-8450-1-git-send-email-eric.auger@redhat.com> <1535026656-8450-10-git-send-email-eric.auger@redhat.com> From: Jean-Philippe Brucker Message-ID: <538a2b88-dec5-a6fa-d918-486284eb56a9@arm.com> Date: Fri, 31 Aug 2018 14:20:34 +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: <1535026656-8450-10-git-send-email-eric.auger@redhat.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 On 23/08/18 13:17, Eric Auger wrote: > if (ste->s1_cfg) { > - BUG_ON(ste_live); Scary! :) The current code assumes that it can make modifications to the STE in any order and enable translation after a sync. So far I haven't been able to find anything that violates this rule in the spec: "If software modifies the structure while it is valid, it must not allow the structure to enter an invalid intermediate state." So maybe it's fine, though to be safe I would have started with disabling the STE (http://www.linux-arm.org/git?p=linux-jpb.git;a=commitdiff;h=936e49f923e101c061269eadd5fa43fef819d2e9) Thanks, Jean