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 3329BC2D0C3 for ; Tue, 17 Dec 2019 01:38:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11409218AC for ; Tue, 17 Dec 2019 01:38:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726320AbfLQBiS (ORCPT ); Mon, 16 Dec 2019 20:38:18 -0500 Received: from mga06.intel.com ([134.134.136.31]:27444 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726016AbfLQBiR (ORCPT ); Mon, 16 Dec 2019 20:38:17 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Dec 2019 17:38:17 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,323,1571727600"; d="scan'208";a="227319645" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga002.jf.intel.com with ESMTP; 16 Dec 2019 17:38:14 -0800 Cc: baolu.lu@linux.intel.com, "Raj, Ashok" , "Kumar, Sanjay K" , "jacob.jun.pan@linux.intel.com" , "Tian, Kevin" , "Sun, Yi Y" , Peter Xu , "iommu@lists.linux-foundation.org" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v3 5/6] iommu/vt-d: Flush PASID-based iotlb for iova over first level To: "Liu, Yi L" , Joerg Roedel , David Woodhouse , Alex Williamson References: <20191211021219.8997-1-baolu.lu@linux.intel.com> <20191211021219.8997-6-baolu.lu@linux.intel.com> <6a5f6695-d1fd-e7d1-3ea3-f222a1ef0e54@linux.intel.com> From: Lu Baolu Message-ID: Date: Tue, 17 Dec 2019 09:37:22 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.1 MIME-Version: 1.0 In-Reply-To: <6a5f6695-d1fd-e7d1-3ea3-f222a1ef0e54@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi again, On 12/17/19 9:19 AM, Lu Baolu wrote: > Hi Yi, > > On 12/15/19 5:22 PM, Liu, Yi L wrote: >> Ok, let me explain more... default pasid is meaningful only when >> the domain has been attached to a device as an aux-domain. right? > > No exactly. Each domain has a specific default pasid, no matter normal > domain (RID based) or aux-domain (PASID based). The difference is for a > normal domain RID2PASID value is used, for an aux-domain the pasid is > allocated from a global pool. > > The same concept used in VT-d 3.x scalable mode. For RID based DMA > translation RID2PASID value is used when walking the tables; For PASID > based DMA translation a real pasid in the transaction is used. > >> If a domain only has one device, and it is attached to this device as >> normal domain (normal domain means non aux-domain here). Then >> you should flush cache with domain-id and RID2PASID value. >> If a domain has one device, and it is attached to this device as >> aux-domain. Then you may want to flush cache with domain-id >> and default pasid. right? > > A domain's counterpart is IOMMU group. So we say attach/detach domain > to/from devices in a group. We don't allow devices with different > default pasid sitting in a same group, right? > >> Then let's come to the case I mentioned in previous email. a mdev >> and another device assigned to a single VM. In host, you will have >> a domain which has two devices, one device(deva) is attached as > > No. We will have two IOMMU groups and two domains. Correct me if my > understanding is not right. Reconsidered this. Unfortunately, my understanding is not right. :-( A single domain could be attached to multiple IOMMU groups. So it comes to the issue you concerned. Do I understand it right? > >> normal domain, another one (devB) is attached as aux-domain. Then >> which pasid should be used when the mapping in IOVA page table is >> modified? RID2PASID or default pasid? I think both should be used >> since the domain means differently to the two devices. If you just >> use default pasid, then deva may still be able to use stale caches. You are right. I will change it accordingly. The logic should look like: if (domain attached to physical device) flush_piotlb_with_RID2PASID() else if (domain_attached_to_mdev_device) flush_piotlb_with_default_pasid() Does this work for you? Thanks for catching this! Best regards, baolu