From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from szxga06-in.huawei.com ([45.249.212.32]:33298 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725908AbeIEHnw (ORCPT ); Wed, 5 Sep 2018 03:43:52 -0400 Subject: Re: [PATCH v2 13/40] vfio: Add support for Shared Virtual Addressing To: Jean-Philippe Brucker , "linux-arm-kernel@lists.infradead.org" , "linux-pci@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "devicetree@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "kvm@vger.kernel.org" , "linux-mm@kvack.org" References: <20180511190641.23008-1-jean-philippe.brucker@arm.com> <20180511190641.23008-14-jean-philippe.brucker@arm.com> <5B83B11E.7010807@huawei.com> <1d5b6529-4e5a-723c-3f1b-dd5a9adb490c@arm.com> <5B89F818.7060300@huawei.com> <3a961aff-e830-64bb-b6a9-14e08de1abf5@arm.com> <5B8DEA15.7020404@huawei.com> CC: "joro@8bytes.org" , Will Deacon , Robin Murphy , "alex.williamson@redhat.com" , "tn@semihalf.com" , "liubo95@huawei.com" , "thunder.leizhen@huawei.com" , "xieyisheng1@huawei.com" , "ilias.apalodimas@linaro.org" , "jonathan.cameron@huawei.com" , "liudongdong3@huawei.com" , "shunyong.yang@hxt-semitech.com" , "nwatters@codeaurora.org" , "okaya@codeaurora.org" , "jcrouse@codeaurora.org" , "rfranz@cavium.com" , "dwmw2@infradead.org" , "jacob.jun.pan@linux.intel.com" , "yi.l.liu@intel.com" , "ashok.raj@intel.com" , "kevin.tian@intel.com" , "baolu.lu@linux.intel.com" , "robdclark@gmail.com" , "christian.koenig@amd.com" , "bharatku@xilinx.com" , "rgummal@xilinx.com" , =?UTF-8?B?57Gz57Gz?= , wangzhou1 , "liguozhu@hisilicon.com" , fanghao11 From: Xu Zaibo Message-ID: <5B8F4A59.20004@huawei.com> Date: Wed, 5 Sep 2018 11:15:37 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Sender: linux-pci-owner@vger.kernel.org List-ID: Hi, On 2018/9/4 18:57, Jean-Philippe Brucker wrote: > On 04/09/2018 03:12, Xu Zaibo wrote: >> On 2018/9/3 18:34, Jean-Philippe Brucker wrote: >>> On 01/09/18 03:23, Xu Zaibo wrote: >>>> As one application takes a whole function while using VFIO-PCI, why do >>>> the application and the >>>> function need to enable PASID capability? (Since just one I/O page table >>>> is enough for them.) >>> At the moment the series doesn't provide support for SVA without PASID >>> (on the I/O page fault path, 08/40). In addition the BIND ioctl could be >>> used by the owner application to bind other processes (slaves) and >>> perform sub-assignment. But that feature is incomplete because we don't >>> send stop_pasid notification to the owner when a slave dies. >>> >> So, Could I understand like this? >> >> 1. While the series are finished well, VFIO-PCI device can be held >> by only one process >> through binding IOCTL command without PASID (without PASID >> being exposed user space). > It could, but isn't supported at the moment. In addition to adding > support in the I/O page fault code, we'd also need to update the VFIO > API. Currently a VFIO_TYPE1 domain always supports the MAP/UNMAP ioctl. > The case you describe isn't compatible with MAP/UNMAP, since the process > manages the shared address space with mmap or malloc. We'd probably need > to introduce a new VFIO IOMMU type, in which case the bind could be > performed implicitly when the process does VFIO_SET_IOMMU. Then the > process wouldn't need to send an additional BIND IOCTL. ok. got it. This is the legacy mode, so all the VFIO APIs are kept unchanged? >> 2. While using VFIO-PCI device to support multiple processes with >> SVA series, a primary >> process with multiple secondary processes must be deployed just >> like DPDK(https://www.dpdk.org/). >> And, the PASID still has to be exposed to user land. > Right. A third case, also implemented by this patch (and complete), is > the primary process simply doing a BIND for itself, and using the > returned PASID to share its own address space with the device. > ok. But I am worried that the sulotion of one primary processes with several secondary ones is a little bit limited. Maybe, users don't want to depend on the primary process. :) Thanks, Zaibo .