From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id CA7E46B5730 for ; Fri, 31 Aug 2018 09:35:17 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id 20-v6so11004769ois.21 for ; Fri, 31 Aug 2018 06:35:17 -0700 (PDT) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id m130-v6si6696749oif.200.2018.08.31.06.35.16 for ; Fri, 31 Aug 2018 06:35:16 -0700 (PDT) Subject: Re: [PATCH v2 13/40] vfio: Add support for Shared Virtual Addressing References: <20180511190641.23008-1-jean-philippe.brucker@arm.com> <20180511190641.23008-14-jean-philippe.brucker@arm.com> <5B83B11E.7010807@huawei.com> From: Jean-Philippe Brucker Message-ID: <1d5b6529-4e5a-723c-3f1b-dd5a9adb490c@arm.com> Date: Fri, 31 Aug 2018 14:34:52 +0100 MIME-Version: 1.0 In-Reply-To: <5B83B11E.7010807@huawei.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Xu Zaibo , 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 Cc: joro@8bytes.org, will.deacon@arm.com, robin.murphy@arm.com, 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 , fanghao11 Hi Zaibo, On 27/08/18 09:06, Xu Zaibo wrote: >> +struct vfio_iommu_type1_bind_process { >> + __u32 flags; >> +#define VFIO_IOMMU_BIND_PID (1 << 0) >> + __u32 pasid; > As I am doing some works on the SVA patch set. I just consider why the > user space need this pasid. > Maybe, is it much more reasonable to set the pasid into all devices > under the vfio container by > a call back function from 'vfio_devices' while > 'VFIO_IOMMU_BIND_PROCESS' CMD is executed > in kernel land? I am not sure because there exists no suitable call back > in 'vfio_device' at present. When using vfio-pci, the kernel doesn't know how to program the PASID into the device because the only kernel driver for the device is the generic vfio-pci module. The PCI specification doesn't describe a way of setting up the PASID, it's vendor-specific. Only the userspace application owning the device (and calling VFIO_IOMMU_BIND) knows how to do it, so we return the allocated PASID. Note that unlike vfio-mdev where applications share slices of a function, with vfio-pci one application owns the whole function so it's safe to let userspace set the PASID in hardware. With vfio-mdev it's the kernel driver that should be in charge of setting the PASID as you described, and we wouldn't have a reason to return the PASID in the vfio_iommu_type1_bind_process structure. Thanks, Jean