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 5D4AEC432C1 for ; Tue, 24 Sep 2019 04:42:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D4A4214AF for ; Tue, 24 Sep 2019 04:42:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394439AbfIXEm3 (ORCPT ); Tue, 24 Sep 2019 00:42:29 -0400 Received: from mga01.intel.com ([192.55.52.88]:41859 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390852AbfIXEm3 (ORCPT ); Tue, 24 Sep 2019 00:42:29 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Sep 2019 21:42:29 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,542,1559545200"; d="scan'208";a="200775783" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by orsmga002.jf.intel.com with ESMTP; 23 Sep 2019 21:42:25 -0700 Cc: baolu.lu@linux.intel.com, Joerg Roedel , David Woodhouse , Alex Williamson , sanjay.k.kumar@intel.com, kevin.tian@intel.com, yi.l.liu@intel.com, yi.y.sun@intel.com, iommu@lists.linux-foundation.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest To: "Raj, Ashok" , Jacob Pan References: <20190923122454.9888-1-baolu.lu@linux.intel.com> <20190923122715.53de79d0@jacob-builder> <20190923202552.GA21816@araj-mobl1.jf.intel.com> From: Lu Baolu Message-ID: Date: Tue, 24 Sep 2019 12:40:29 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190923202552.GA21816@araj-mobl1.jf.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, On 9/24/19 4:25 AM, Raj, Ashok wrote: > Hi Jacob > > On Mon, Sep 23, 2019 at 12:27:15PM -0700, Jacob Pan wrote: >>> >>> In VT-d 3.0, scalable mode is introduced, which offers two level >>> translation page tables and nested translation mode. Regards to >>> GIOVA support, it can be simplified by 1) moving the GIOVA support >>> over 1st-level page table to store GIOVA->GPA mapping in vIOMMU, >>> 2) binding vIOMMU 1st level page table to the pIOMMU, 3) using pIOMMU >>> second level for GPA->HPA translation, and 4) enable nested (a.k.a. >>> dual stage) translation in host. Compared with current shadow GIOVA >>> support, the new approach is more secure and software is simplified >>> as we only need to flush the pIOMMU IOTLB and possible device-IOTLB >>> when an IOVA mapping in vIOMMU is torn down. >>> >>> .-----------. >>> | vIOMMU | >>> |-----------| .-----------. >>> | |IOTLB flush trap | QEMU | >>> .-----------. (unmap) |-----------| >>> | GVA->GPA |---------------->| | >>> '-----------' '-----------' >>> | | | >>> '-----------' | >>> <------------------------------ >>> | VFIO/IOMMU >>> | cache invalidation and >>> | guest gpd bind interfaces >>> v >> For vSVA, the guest PGD bind interface will mark the PASID as guest >> PASID and will inject page request into the guest. In FL gIOVA case, I >> guess we are assuming there is no page fault for GIOVA. I will need to >> add a flag in the gpgd bind such that any PRS will be auto responded >> with invalid. > > Is there real need to enforce this? I'm not sure if there is any > limitation in the spec, and if so, can the guest check that instead? For FL gIOVA case, gPASID is always 0. If a physical device is passed through, hPASID is also 0; If an mdev device (representing an ADI) instead, hPASID would be the PASID corresponding to the ADI. The simulation software (i.e. QEMU) maintains a map between gPASID and hPASID. I second Ashok's idea. We don't need to distinguish these two cases in the api and handle page request interrupt in guest as an unrecoverable one. > > Also i believe the idea is to overcommit PASID#0 such uses. Thought > we had a capability to expose this to the vIOMMU as well. Not sure if this > is already documented, if not should be up in the next rev. > > >> >> Also, native use of IOVA FL map is not to be supported? i.e. IOMMU API >> and DMA API for native usage will continue to be SL only? >>> .-----------. >>> | pIOMMU | >>> |-----------| >>> .-----------. >>> | GVA->GPA |<---First level >>> '-----------' >>> | GPA->HPA |<---Scond level > > s/Scond/Second Yes. Thanks! Best regards, Baolu