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 3DF2FC43603 for ; Tue, 17 Dec 2019 04:13:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14F07206E6 for ; Tue, 17 Dec 2019 04:13:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726772AbfLQENk (ORCPT ); Mon, 16 Dec 2019 23:13:40 -0500 Received: from mga14.intel.com ([192.55.52.115]:45244 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725836AbfLQENk (ORCPT ); Mon, 16 Dec 2019 23:13:40 -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 fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 Dec 2019 20:13:37 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,324,1571727600"; d="scan'208";a="227349930" Received: from blu2-mobl3.ccr.corp.intel.com (HELO [10.254.215.47]) ([10.254.215.47]) by orsmga002.jf.intel.com with ESMTP; 16 Dec 2019 20:13:36 -0800 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 Cc: "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" 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 12:13:35 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Hi, On 2019/12/17 10:36, Liu, Yi L wrote: >> From: Liu, Yi L >> Sent: Tuesday, December 17, 2019 10:26 AM >> To: Lu Baolu ; Joerg Roedel ; David >> Woodhouse ; Alex Williamson >> >> Subject: RE: [PATCH v3 5/6] iommu/vt-d: Flush PASID-based iotlb for iova over first >> level >> >>> From: Lu Baolu [mailto:baolu.lu@linux.intel.com] >>> Sent: Tuesday, December 17, 2019 9:37 AM >>> To: Liu, Yi L ; Joerg Roedel ; David >>> Woodhouse ; Alex Williamson >>> >>> Subject: Re: [PATCH v3 5/6] iommu/vt-d: Flush PASID-based iotlb for iova over first >>> level >>> >>> 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? >> yes. Device within the same group has no such issue since such >> devices are not able to enabled aux-domain. Now our understanding >> are aligned. :-) >> >>>>> 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! >> If no else, it would work for scalable mode. ^_^ I noticed you've >> already corrected by yourself in another reply. :-) Look forward to >> your next version. > BTW. The discussion in this thread may apply to other cache flush > in your series. Please have a check. At least, there are two places which > need to be updated in this single patch. Sure. I will. Best regards, baolu > > Regards, > Yi Liu