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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 E1695C433DF for ; Mon, 25 May 2020 10:21:58 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AF06020723 for ; Mon, 25 May 2020 10:21:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SKCvYhx6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AF06020723 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:48356 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jdAF3-0001Is-RM for qemu-devel@archiver.kernel.org; Mon, 25 May 2020 06:21:57 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51696) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jdADn-0008BL-Al for qemu-devel@nongnu.org; Mon, 25 May 2020 06:20:39 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:32784 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jdADl-0006U4-Iz for qemu-devel@nongnu.org; Mon, 25 May 2020 06:20:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590402036; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JRfSNC2ss3HIXRt1DQWODzcZm5cBs0oerm7Xf2BMQvc=; b=SKCvYhx6yo0821TdA0dHaW0svqQTPRBy1vs0fYRWZCvxnFFst3Nb3YipivUQo7l3sfReTt GvWisRa0WXUzo/3osbe9g6BhtNvsMk+HDHKr+9KEA/7RRybJXykqYXxa2bnCmnW61hh+lK 0lHDVzfGSDmQDyorVRm9o0boVqfh2SM= Received: from mail-ej1-f71.google.com (mail-ej1-f71.google.com [209.85.218.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-472-h12viYhCMC2lNoaGV_pYAw-1; Mon, 25 May 2020 06:20:34 -0400 X-MC-Unique: h12viYhCMC2lNoaGV_pYAw-1 Received: by mail-ej1-f71.google.com with SMTP id qn27so6243828ejb.11 for ; Mon, 25 May 2020 03:20:34 -0700 (PDT) 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=JRfSNC2ss3HIXRt1DQWODzcZm5cBs0oerm7Xf2BMQvc=; b=AWtRLv4jtu5sS99cUMxaOTkbocZSxjgfA+VcAA1NL/lK+LPctHksXgGLTQ8T1Kw+/q 3cwl+abl+zltmLwVTfV1uAK/LmhceHbdq4kBZA1i0MJUZ5LjX2kEwxj//+nRXsYDck3h plvoBJW9n7w8IN1NR6aR5ziBPPoGYYLSbYnV4QxXHVEmILmRxzExcFcmjca6BQ0xO132 tXuEh1if9BG+DI1Nn0gNSYyqdQkR08ty9+lpuVnyhAlj4mhn9s6FcRNbku9BeLixGj2G VHOKhUiJQOV5d0BVhZTDnDE4SOUNenIm/SOPO45GL4cGkLk3pPP1GsY7zZ4PHO61EKqC Qz+Q== X-Gm-Message-State: AOAM531BprL8AQP5jnCmTsGLRk6fm1mvDwuqnQiuys8XOANFTmNDZvhc 00EvYamoGAea5GsKTZOobnokq/gMlhVHIzF3O0DSrGa7E411qE7vO/h5dQDzF8MjlobFXDEtf20 vIyTwUn64s4dEZoA= X-Received: by 2002:aa7:d39a:: with SMTP id x26mr13924175edq.207.1590402033135; Mon, 25 May 2020 03:20:33 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzNwbP/LQMpyhYdJQA8XtYTkL0MUYeSgkOMEblZiq1QIasG6dQW4eY/bg2rd+tlZv/EVawAwA== X-Received: by 2002:aa7:d39a:: with SMTP id x26mr13924159edq.207.1590402032941; Mon, 25 May 2020 03:20:32 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:3c1c:ffba:c624:29b8? ([2001:b07:6468:f312:3c1c:ffba:c624:29b8]) by smtp.gmail.com with ESMTPSA id w8sm15521648edu.15.2020.05.25.03.20.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 25 May 2020 03:20:32 -0700 (PDT) Subject: Re: [PATCH v6 1/3] memory: drop guest writes to read-only ram device regions To: Yan Zhao References: <20200430080744.31232-1-yan.y.zhao@intel.com> <20200430080946.31286-1-yan.y.zhao@intel.com> <9dd7f00b-1199-1097-80d4-1b700c0f28d6@redhat.com> <20200525011853.GB8867@joy-OptiPlex-7040> From: Paolo Bonzini Message-ID: Date: Mon, 25 May 2020 12:20:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200525011853.GB8867@joy-OptiPlex-7040> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=pbonzini@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/25 01:44:10 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Alex Williamson , xin.zeng@intel.com, QEMU Developers , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 25/05/20 03:18, Yan Zhao wrote: > On Thu, May 21, 2020 at 04:38:47PM +0200, Paolo Bonzini wrote: >> On 30/04/20 11:40, Peter Maydell wrote: >>>> This does not "drop" a write to a r/o region -- it causes it to generate >>>> whatever the guest architecture's equivalent of a bus error is (eg data >>>> abort on Arm). >> >> >>> More generally, this change seems a bit odd: currently we do not >>> check the mr->readonly flag here, but in general guests don't get >>> to write to ROM areas. Where is that check currently done >> >> Writes to ROM are directed to mr->ops unassigned_mem_ops. Because _all_ >> ram-device reads and writes go through the ops, for ram-device we have >> to stick the check for mr->readonly in the ops. >> >> On one hand, I was quite surprised to see that unassigned_mem_write does >> not return MEMTX_ERROR now that I looked at it. >> >> On the other hand, we should use MEMTX_ERROR in patch 2 as well, if we >> decide it's the way to go. >> >> (Sorry Yan for the late response). >> > hi Paolo, > thanks for your reply and never mind :) > > But there's one thing I just can't figure out the reason and eagerly need > your guide. > > why do we have to convert all .write operations to .write_with_attrs and > return MEMTX_ERROR? because of the handling of writes to read-only region? Not all of them, only those that need to return MEMTX_ERROR. I would like some guidance from Peter as to whether (or when) reads from ROMs should return MEMTX_ERROR. This way, we can use that information to device what the read-only ram-device regions should do. Paolo