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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 57F74C433B4 for ; Tue, 27 Apr 2021 06:56:45 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 094A361076 for ; Tue, 27 Apr 2021 06:56:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 094A361076 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.118032.223992 (Exim 4.92) (envelope-from ) id 1lbHe4-0007dh-EC; Tue, 27 Apr 2021 06:56:32 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 118032.223992; Tue, 27 Apr 2021 06:56:32 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lbHe4-0007da-BC; Tue, 27 Apr 2021 06:56:32 +0000 Received: by outflank-mailman (input) for mailman id 118032; Tue, 27 Apr 2021 06:56:31 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lbHe3-0007dV-2g for xen-devel@lists.xenproject.org; Tue, 27 Apr 2021 06:56:31 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 6f715d80-4288-417f-b627-7e262185731c; Tue, 27 Apr 2021 06:56:30 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 48CFDAF88; Tue, 27 Apr 2021 06:56:29 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 6f715d80-4288-417f-b627-7e262185731c X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1619506589; h=from:from:reply-to: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=pjGui25wUiC5sijz/4iOg+LwF5L69MBvHR4cTMbP3VI=; b=PWtwKxhHVa7RiNpR8dpGaFFzz7cQepGl+yCcwytfAfFw8gj5sgQ6k+nfVCK6N+wDefjfgl VU+3aPOATlWDipbaLpBCfS5ookNFwmO7JA3u3R75ef1thBxN53MzJExwwP/+T9eg3JpXxt If7Rms4bT7zfUmStj/4FGKTVbuc7fA4= Subject: Re: [RFC PATCH] iommu: make no-quarantine mean no-quarantine To: Scott Davis Cc: Scott Davis , Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini , Wei Liu , Paul Durrant , xen-devel@lists.xenproject.org References: <0a292d952ff71dbfed5234d27b42a05f7b49a1fe.1619451434.git.scott.davis@starlab.io> From: Jan Beulich Message-ID: Date: Tue, 27 Apr 2021 08:56:28 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <0a292d952ff71dbfed5234d27b42a05f7b49a1fe.1619451434.git.scott.davis@starlab.io> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 26.04.2021 19:25, Scott Davis wrote: > This patch modifies Xen's behavior when making devices assignable while the > iommu=no-quarantine command line option is in effect. Currently this option > only affects device deassignment, causing devices to get immediately assigned > back to Dom0 instead of to the quarantine dom_io domain. This patch extends > no-quarantine to device assignment as well, preventing devices from being > assigned to dom_io when they are made assignable while no-quarantine is in > effect. Well, the term "quarantine" to me means a safety action taken _after_ possible exposure to something "bad". Therefore I see this being specific to device de-assignment as the logical thing. Hence if a mode like what you describe was wanted, I don't think it should be the result of "iommu=no-quarantine". > First patch submission, apologies in advance for any formatting or other errors. I couldn't spot any, except maybe ... > Background: I am setting up a QEMU-based development and testing environment for > the Crucible team at Star Lab that includes emulated PCIe devices for > passthrough and hotplug. I encountered an issue with `xl pci-assignable-add` > that causes the host QEMU to rapidly allocate memory until getting OOM-killed. > I then found that the issue could be worked around either by using manual sysfs > commands to rebind devices to pciback or by skipping over the quarantine logic > in `libxl__device_pci_assignable_add`, producing a working system. I hoped that > setting iommu=no-quarantine on the command line would have the same effect, only > to be surprised that it did not. ... some of this "why do we want this" would belong in the commit message imo, not just here. Jan