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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 225DBC433E0 for ; Wed, 10 Feb 2021 04:07:03 +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 8611164E3E for ; Wed, 10 Feb 2021 04:07:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8611164E3E 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]:40984 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l9gmL-0001h7-LK for qemu-devel@archiver.kernel.org; Tue, 09 Feb 2021 23:07:01 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:54308) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l9glI-0001H9-J9 for qemu-devel@nongnu.org; Tue, 09 Feb 2021 23:05:56 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:29777) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l9glF-0006e7-DP for qemu-devel@nongnu.org; Tue, 09 Feb 2021 23:05:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612929951; 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=+eeJUlvc0pnXLjpnDCtbkfnnf8iLNikSvzBpTdlDUiw=; b=OyIMwAuOZTrkl/YAseaEhwZv1AI4dAyY12ihn6znIYBdKsGKfLTLbLuaYIcIwlhxVhWqZ4 5k8PazjYysBfEdCqUxf/TzRyntCgg6IX3/CX2Tp4/ljQozXfWnTv2V4z0tRVgF8QpbY8Ky JBhFqldZ/zTBbs6z4CvGq7xKN+eJed8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-345-zTih6tZoOXCF8TKIDHza2g-1; Tue, 09 Feb 2021 23:05:49 -0500 X-MC-Unique: zTih6tZoOXCF8TKIDHza2g-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 343C5107ACE6; Wed, 10 Feb 2021 04:05:48 +0000 (UTC) Received: from [10.72.12.223] (ovpn-12-223.pek2.redhat.com [10.72.12.223]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1592060C4D; Wed, 10 Feb 2021 04:05:34 +0000 (UTC) Subject: Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support To: Peter Xu , "Tian, Kevin" References: <20210204191228.187550-1-peterx@redhat.com> <2382a93d-41c1-24fd-144f-87ee18171bc9@redhat.com> <213acf9a-d1c0-3a1d-4846-877d90fadc03@redhat.com> <20210205153107.GX6468@xz-x1> <20210207144715.GG3195@xz-x1> <20210208182607.GA68242@xz-x1> From: Jason Wang Message-ID: <5cfe00bd-7cc3-c1f7-8dfd-3781a289357a@redhat.com> Date: Wed, 10 Feb 2021 12:05:33 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210208182607.GA68242@xz-x1> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=jasowang@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Received-SPF: pass client-ip=216.205.24.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.57, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.265, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: Jean-Philippe Brucker , Auger Eric , "Michael S . Tsirkin" , "qemu-devel@nongnu.org" , Eugenio Perez Martin Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2021/2/9 上午2:26, Peter Xu wrote: > Kevin, > > On Mon, Feb 08, 2021 at 07:03:08AM +0000, Tian, Kevin wrote: >> It really depends on the definition of dev-iotlb in this context. To me the >> fact that virtio-iommu needs to notify the kernel for updating split cache >> is already sort of dev-iotlb semantics, regardless of whether it's delivered >> through a iotlb message or dev-iotlb message in a specific implementation. 😊 > Yeah maybe it turns out that we'll just need to implement dev-iotlb for > virtio-iommu. Note that on top of device-IOTLB, device may choose to implement an IOMMU which support #PF. In this case, dev-iotlb semantic is not a must. (Or it can co-operate with things like ATS if driver wants) Virtio will probably provide this feature in the future. Thanks > > I am completely fine with that and I'm never against it. :) I was throwing out > a pure question only, because I don't know the answer. > > My question was majorly based on the fact that dev-iotlb and iotlb messages > really look the same; it's not obvious then whether it would always matter a > lot when in a full emulation environment. > > One example is current vhost - vhost previously would work without dev-iotlb > (ats=on) because trapping UNMAP would work too for vhost to work. It's also > simply because at least for VT-d the driver needs to send both one dev-iotlb > and one (probably same) iotlb message for a single page invalidation. The > dev-iotlb won't help a lot in full emulation here but instead it slows thing > down a little bit (QEMU has full knowledge as long as it receives either of the > message). > > Thanks, >