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=-2.2 required=3.0 tests=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 73320C3A589 for ; Tue, 20 Aug 2019 05:23:36 +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 488DF216F4 for ; Tue, 20 Aug 2019 05:23:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 488DF216F4 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]:33082 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hzwcJ-0002Zy-DJ for qemu-devel@archiver.kernel.org; Tue, 20 Aug 2019 01:23:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58818) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1hzwbg-0002A2-WB for qemu-devel@nongnu.org; Tue, 20 Aug 2019 01:22:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hzwbf-0007HW-Jz for qemu-devel@nongnu.org; Tue, 20 Aug 2019 01:22:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56866) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hzwbf-0007HO-CI for qemu-devel@nongnu.org; Tue, 20 Aug 2019 01:22:55 -0400 Received: from mail-pf1-f199.google.com (mail-pf1-f199.google.com [209.85.210.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 44FBD3CA13 for ; Tue, 20 Aug 2019 05:22:54 +0000 (UTC) Received: by mail-pf1-f199.google.com with SMTP id 22so4002374pfn.22 for ; Mon, 19 Aug 2019 22:22:54 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=lmDZdJpZ36GD1TZ3IZlgYRWs9MNglSdkq9RFiVWupgY=; b=LCjMte6QoQ43ewh+xpGy2etweH7hDlLIpLkX2rm6FDfMH3XqdoiCO7Hf1jtmzCSFFz MedFBlkhfbHqM+SQW4UtCN8DWnL/W7YDotiIYln0YrvTIKgQYxJMxcToR/7vzaZdbrin VYu7r101SqmSFHltqYMTUQbDCSh13LcI6S++TTPLIIQgHdedHOSCQzDH/olTb24Yl7Em aq9XP/WDLeOkTCEwA8IkcpLnER3VkSrJUBnLBosLuTff37hSsC5tC3twDR/VAce2kSpH Ei/i0ydgjKYgXp0sG/JOcqpCpi3fWS3qeSarOl9ir7m38T7Nv+S00cepaf4JONCwLeJe fIGA== X-Gm-Message-State: APjAAAUu+GBBin1Aagq4hu5yZ6laZD7WQhiiwUbHiIPYa3KSRblkL1f8 qVlZfdxlQrfUdJ5OMupCsT254cIum30WiU/L8g35Mcu+khaMs/cXYpLGenWWa4FurcBoLNMoidX UGfzWoN2S5g6aIqk= X-Received: by 2002:a17:902:9889:: with SMTP id s9mr26795728plp.100.1566278573260; Mon, 19 Aug 2019 22:22:53 -0700 (PDT) X-Google-Smtp-Source: APXvYqxK5J4m8yUjriMIG+1eJrHa8fayi8hmKhNFWFO5aRjv7HZi78R618R9Vno3nZRfMR2UIqdYZg== X-Received: by 2002:a17:902:9889:: with SMTP id s9mr26795713plp.100.1566278573096; Mon, 19 Aug 2019 22:22:53 -0700 (PDT) Received: from xz-x1 ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id e26sm20126624pfd.14.2019.08.19.22.22.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Aug 2019 22:22:52 -0700 (PDT) Date: Tue, 20 Aug 2019 13:22:40 +0800 From: Peter Xu To: qemu-devel@nongnu.org Message-ID: <20190820052240.GG13560@xz-x1> References: <20190812074531.28970-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190812074531.28970-1-peterx@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH RFC 0/4] intel_iommu: Do sanity check of vfio-pci earlier 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: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , Eduardo Habkost , "Michael S. Tsirkin" , Jason Wang , Alex Williamson , Bandan Das , Igor Mammedov , Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Aug 12, 2019 at 09:45:27AM +0200, Peter Xu wrote: > This is a RFC series. > > The VT-d code has some defects, one of them is that we cannot detect > the misuse of vIOMMU and vfio-pci early enough. > > For example, logically this is not allowed: > > -device intel-iommu,caching-mode=off \ > -device vfio-pci,host=05:00.0 > > Because the caching mode is required to make vfio-pci devices > functional. > > Previously we did this sanity check in vtd_iommu_notify_flag_changed() > as when the memory regions change their attributes. However that's > too late in most cases! Because the memory region layouts will only > change after IOMMU is enabled, and that's in most cases during the > guest OS boots. So when the configuration is wrong, we will only bail > out during the guest boots rather than simply telling the user before > QEMU starts. > > The same problem happens on device hotplug, say, when we have this: > > -device intel-iommu,caching-mode=off > > Then we do something like: > > (HMP) device_add vfio-pci,host=05:00.0,bus=pcie.1 > > If at that time the vIOMMU is enabled in the guest then the QEMU > process will simply quit directly due to this hotplug event. This is > a bit insane... > > This series tries to solve above two problems by introducing two > sanity checks upon these places separately: > > - machine done > - hotplug device > > This is a bit awkward but I hope this could be better than before. > There is of course other solutions like hard-code the check into > vfio-pci but I feel it even more unpretty. I didn't think out any > better way to do this, if there is please kindly shout out. > > Please have a look to see whether this would be acceptable, thanks. Any more comment on this? Thanks, -- Peter Xu